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Hind genotype influences on lactation and calf growth in farmed red deer (Cervus elaphus)
Livestock Science 170 (2014) 172–180
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Hind genotype influences on lactation and calf growth in farmed red deer (Cervus elaphus) D.R. Stevens a,n, J.A. Archer a, G.W. Asher a, J.F. Ward a, I.C. Scott a, K.T. O’Neill a, R.P. Littlejohn a, G.K. Barrell b a b
AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand Lincoln University, Agriculture and Life Sciences Division, PO Box 84, Canterbury 8150, New Zealand
a r t i c l e in f o
abstract
Article history: Received 18 May 2014 Received in revised form 17 September 2014 Accepted 20 September 2014
Multiparous red deer (Cervus elaphus scoticus) hinds (n ¼ 18) were artificially inseminated with semen from a red deer stag (n ¼8) or wapiti bull (C.e. nelsoni) (n ¼ 10) to produce red deer or F1 crossbred (C.e. scoticus C.e. nelsoni) calves. A further seven wapiti red deer (F1) hinds were artificially inseminated with semen from an unrelated F1 stag to test the hypotheses that (1) crossbred hinds rearing crossbred calves will produce more milk to support calf growth than red deer hinds rearing crossbred calves, and (2) the extra lactation demand of crossbred calves will exert a more detrimental effect on red deer hind live weight and body condition than would occur if the dam was a crossbred hind. Hinds and calves were grazed on ryegrass and white clover pastures and supplemented with pasture silage and barley grain when pasture supply was inadequate. Calves were left with their mothers until approximately 240 days of age. Mean body condition score (BCS) was lower in F1 hinds rearing F2 calves during late lactation (days 150 to 240, P o 0.05) than red deer hinds rearing either red deer or F1 calves. F1 calves grew significantly faster than red deer calves and were heavier at all ages, while F2 calves were intermediate. Milk intake of both F1 and F2 calves was higher than red deer calves until day 76 of lactation (P 4 0.05), but similar thereafter. Male calves had a higher milk intake than female calves at 20 days of age only (P ¼ 0.004). The average hind pasture intake was greatest in F1 hinds rearing F2 calves, intermediate in red deer hinds rearing F1 calves and lowest in red deer hinds rearing red deer calves (P ¼ 0.038). Total milk output for the lactation increased by approximately 14.6 kg/kg average calf live weight at weaning for both F1 hinds rearing F2 calves (P ¼ 0.008) and red deer hinds rearing red deer calves (P¼ 0.072), suggesting that calf demand rather than hind liveweight was the key determinant of lactation performance. This was not the case for red deer hinds rearing F1 calves suggesting that there is an upper limit to lactation output depending on hind size. These results do not support the hypothesis that a crossbred hind rearing a crossbred calf will produce more milk than a red deer hind rearing a crossbred calf and provides evidence that the milk production of the hind is primarily driven by milk demand of the calf but has an upper limit depending on the size of the hind. The second hypothesis was not supported as F1 hinds rearing F2 calves exhibited greater loss of body condition score relative to the red deer hinds rearing either red deer or F1 calves in this study. This suggests that the additional energetic demands on a hind from feeding an F1 calf may be met with adequate nutrition. & 2014 Elsevier B.V. All rights reserved.
Keywords: Red deer Crossbreds Lactation Intake Growth
n
Corresponding author. Tel.: þ64 3 4899035. E-mail address: [email protected] (D.R. Stevens).
http://dx.doi.org/10.1016/j.livsci.2014.09.019 1871-1413/& 2014 Elsevier B.V. All rights reserved.
D.R. Stevens et al. / Livestock Science 170 (2014) 172–180
1. Introduction Venison production systems in New Zealand generally aim to produce red deer stags for slaughter in their first year of life to meet the premium chilled venison markets in Europe during the period of traditional venison consumption (Pearse and Fung, 2007). Achieving this requires fast growing animals to meet specified carcass weights by 7–11 months of age. The period of greatest differential between average and potential stag growth performance on New Zealand deer farms occurs during the first six months of the deer’s life. This coincides with the suckling period, indicating that lactation performance of hinds contributes significantly to production (Stevens and Corson, 2003). Accordingly, it is of interest to better understand the drivers of calf growth over this period, including factors influencing lactation. One major driver of calf growth potential is genotype. In New Zealand deer farming, a terminal-sire system is commonly practiced, using stags with a high content of wapiti genes (red deer subspecies of North American origin Cervus elaphus manitobensis, nelsoni, roosevelti) to mate New Zealand red hinds (NZ red) of English and Scottish origins (Cervus elaphus scoticus). The resulting crossbred calves have higher growth rates than calves sired by red deer stags (Pearse, 1992), and so overall productive outputs are considerably higher. However, the mechanisms which support these higher growth rates are poorly understood. What is the major driver of calf growth during lactation—calf demand for milk, or milk supply? In a previous paper (Archer et al., 2013) the impact of calf genotype on the lactation output from hinds of a single genotype (C.e. scoticus) was described. That experiment investigated the question of whether hind lactation is influenced by calf genotype and concluded that red deer hinds rearing crossbred calves produced more milk than red deer hinds rearing red deer calves. This paper addresses the opposite effect of calf genotype—what is the effect of dam genotype on lactation output? How much milk will a crossbred hind produce when raising a crossbred calf, compared with a red deer hind raising a crossbred calf? Does the importance of calf milk demand vs. hind milk supply change over the course of lactation as the calf becomes less dependent on milk? What is the balance of the calf’s diet of milk and pasture and how does this change over the lactation period? What are the implications for hinds of different genotypes
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rearing a calf of a similar genotype in terms of live weight and body condition? The contrast in growth potential of wapiti-cross and red deer calf genotypes offers a useful model to better understand the drivers of lactation performance in deer. Moreover a similar contrast in maternal genotype may provide additional insight to these factors. This paper reports on studies conducted using this model to quantify lactation outputs in deer farmed in New Zealand and relate this to calf growth and impacts on the hind. The hypotheses tested are as follows: (1) Crossbred hinds rearing crossbred calves will produce more milk to support calf growth than red deer hinds rearing crossbred calves. (2) The extra lactation demand of crossbred calves will exert a more detrimental impact on red deer hind live weight and body condition than would occur if the dam was a crossbred hind.
2. Materials and methods 2.1. Animals and management The study was conducted on a cohort of calves born at the Invermay Agricultural Centre (Mosgiel, New Zealand) in November/December 2004. All experimental procedures had prior approval from the Invermay Animal Ethics committee. A total of 18 multiparous red deer hinds of “New Zealand red deer” breeding (predominantly derived from C.e. scoticus) produced calves from artificial insemination with semen from a single red deer (n¼ 8) or wapiti (C.e. nelsoni) sire (n ¼10). In addition, a further seven wapiti red deer (F1) hinds produced calves from insemination with semen from an unrelated wapiti red deer (F1) stag to generate calves with 50% wapiti parentage (F2); i.e. hinds with 50% wapiti parentage rearing calves with 50% wapiti parentage.. Artificial insemination was performed following oestrous synchronisation according to the procedures described by Rhodes et al. (2003). All hinds raised calves the previous season. Table 1 contains a summary of the hind and calf genotype combinations which were used in subsequent experimentation. Calves were born from 21 November to 7 December. Hinds and calves were grazed on predominantly ryegrass (Lolium perenne) pastures and were supplemented
Table 1 Experimental design, calving date, calf birth weight, post-calving hind live weight (LW) and hind LW change in late lactation (day 75 to day 200 after mean calving date). Treatment Hind genotype Sire genotype Calf genotype n Mean birth date (range) Mean gestation length (d) Mean calf birth weight (kg) Mean hind live weight (kg) Hind LW change late lactation (kg)
NZ red NZ red NZ red 8 26 Nov ( 71.35) 232 (7 1.35) 9.9 ( 7 0.24) 111.7 ( 7 2.7) 3.4 ( 7 2.9)
NZ red Wapiti F1 10 3 Dec ( 71.21) 239 ( 71.21) 11.3(7 0.40) 117.3 ( 72.9) 2.1 ( 7 2.8)
NZ red Wapiti NZ red Wapiti F2 7 2 Dec ( 7 1.42) 238 ( 7 1.42) 12.7( 70.78) 170.4 ( 72.6) 9.4 ( 73.0)
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with pasture silage and barley grain (approximately 0.5 kg grain/head/d) when pasture supply was inadequate during winter. Hinds were checked daily during the calving period and birth date, birth weight of calves and calfdam matches were recorded. Calves were weaned in late May 2005 to match the practice of “post-rut weaning” which is used by a significant proportion of New Zealand deer farmers. 2.2. Measurements Live weights of hinds were recorded from 28 October during pregnancy at approximately 2 weekly intervals until the end of the experiment on 30 May 2005. At each weighing an udder score (US) on a 0–5 scale (after Asher et al., 1994) was recorded, where 0 equates to no palpable mammary development and 5 represents a fully engorged udder. Hinds were also assessed for body condition score (BCS) (Audige et al., 1998), with a score of 1 representing an emaciated animal and 5 representing an obese animal. Calves were weighed at birth, and then at approximately 2 week intervals throughout lactation. Measurements of milk intake by the calves and pasture intake by the hinds were made on 16 December, 7 January, 3 February, 3 March and 25 May following the protocols outlined by Archer et al. (2013). Briefly, milk intake measurements were conducted using the double isotope dilution technique (Dove, 1988) over a five day period. Concentrations of tritium and deuterium isotopes were analysed in serum of hinds and calves taking account of the growth of the body water pool of the calf (Dove and Freer, 1979) and for the concentration of deuterium in water entering the body water pool of calves from the outside environment. Analysis of dry matter content of milk was performed on milk samples after thawing and homogenising. Milk samples were weighed and then dried by freeze-dry lyophilisation for 48 h. Remaining solids content was reweighed and the results used to calculate the solids content of individual milk samples. Solids content and milk water intake (from calculations described above) were then used to calculate total milk intake (water plus solids) corrected to 22% solids (representing the approximate average DM of samples obtained). 2.3. Hind and calf pasture intake measurements Pasture intake was calculated using the C32-alkane dilution method (Dove and Mayes, 1996). Hinds were orally dosed daily for 7 consecutive days with 100 mg of n-dotriacontane (C32) powder (Nufarm Health and Sciences NZ, Auckland, NZ) suspended in 5 mL of food grade canola oil on four occasions during lactation with the first collection on 20 and 21 January, being 51 days after mean calving date. The initiation of each treatment period coincided with the final day (Day 5) of each milk measurement period. After the final daily dosing and on the following day 40 g of faecal sample was collected directly from the rectum of each animal. Faecal samples were frozen at 20 1C and later freeze dried and ground for analysis. A plucked sample of pasture, representative of
that eaten was also collected at this time, frozen and then later freeze dried. Analysis for C31, C32, C33, and C35 alkane concentrations was undertaken by the Department of Animal and Veterinary Science analytical laboratory, Lincoln University, using the technique of Mayes et al. (1986), with the modification that samples were digested in an oven at 90 1C instead of on a heating block. Intake was calculated by the alkane dilution in faeces (Dove and Mayes, 1991), as the mean of that calculated from C31:C32 and C33:C32 ratios. Apparent dry matter digestibility was also calculated (Dove and Mayes, 1991) (Digestibility¼ 1 (herbage alkane concentration/faeces alkane concentration) as the mean value of the value calculated using C33 and C35). 2.4. Calculated energy intakes Gross energy intake of calves from milk was calculated by applying a factor of 6.125 MJ per kg of milk intake adjusted to 22% DM. This factor was obtained by applying the energy content equation of (Landete Castillejos et al., 2003) to the milk composition parameters at week 2 of lactation (Landete Castillejos et al., 2000). The gross energy intake was converted to a metabolisable energy intake by multiplying by a factor of 0.95 (Blaxter, 1952). Energy intake of calves and hinds from pasture was calculated from the digestibility of the diet (ME (MJ)¼ 18.4 DMD 0.81; (ARC, 1980)). The energy requirements of both hinds and calves was calculated using the following derived equations (NRC, 2006). Hind energy requirement ¼ 0:544BW0:75 þ ðMilk energy 0:65Þ Adjustments were made for live weight gain (LWG) or live weight loss (LWL) (NRC, 2006). Additional requirement for gain ¼ LWGðkgÞ:54:8 MJME=kg Reduction in requirement for loss ¼ LWL ðkgÞ 18MJME=kg Calf requirements were calculated using a coefficient for maintenance (Archer et al., 2013) from a previous experiment using similar red deer genotypes, and a coefficient for gain (NRC, 2006). Calf energy requirement ¼ 0:741:BW0:75 þgain ðkgÞ 22:3MJME
2.5. Statistical analysis Milk intake, milk solids, feed intake and water turn over (hind and calf) data were analysed in two ways. First, data at each sample time were analysed using the general linear model, fitting calf birth date as a covariate and then adding calf breed and calf sex as fixed effects. Calf birth date was only significant as a covariate for the first two periods and so was dropped from the model thereafter. Secondly, data for all times were analysed by residual maximum likelihood (REML), fitting calf birth date as a covariate, date (as a continuous variable), and calf breed
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and the interaction of calf breed and date, with a term for date. This method was also repeated using calf age in place of date, but this gave no additional insights. Data (apart from live weight, BCS and US) is reported to correspond to the final date of each milk measurement, being days 20, 51, 76, 104, and 197 of age using the mean calving date of 30 November. Calf live weight gain was calculated to represent each intake measurement period by applying linear regression to the live weights that were collected around the time of measurement. Values presented for calf data from the first two periods are adjusted for birth date. Total lactation output from the hinds was calculated by multiplying the number of days between each measurement date by the arithmetic mean of the measurements made at each date. So, for example, the number of days in the first period (20 days) was multiplied by the mean of Day 0 (start of lactation) and the measured milk yield at day 20 to calculate the milk production for that period. Linear regression was used to compare milk yield to post-calving hind live weight and to the average calf live weight (as the arithmetic mean, weighted for the days in each period) applying calf genotype as a grouping factor. 3. Results 3.1. General A summary of the experimental design and key statistics of birth dates and hind live weights is given in Table 1. F1 and F2 calves were associated with longer gestation lengths and, hence, later birth dates than for red deer calves, and were also heavier at birth (Table 1). Milk dry matter concentration averaged 22.8, 22.2 and 22.2 g DM/100 g (sed ¼0.89 g DM/100 g) from hinds rearing red, F1 and F2 calves respectively. Milk dry matter concentration increased during the lactation being 21.1, 21.6, 21.6, 23.7 and 24.1 g DM/100 g (sed ¼0.85 g DM/ 100 g) at days 20, 51, 76, 104 and 197, respectively. The gender of the calf did not influence milk solids concentration. The milk solids concentration from red hinds and the larger red wapiti hinds was similar throughout. 3.2. Hind live weight, BCS, US and intake Mean hind live weight was much higher for F1 hinds rearing F2 calves than for the other genotypes (P o0.001; Fig. 1a), and declined somewhat more for this group during late lactation (Po0.05; Table 1). Mean hind BCS values are presented in Fig. 1b. There was no main effect of calf genotype on hind BCS, but a significant interaction between calf genotype and time was evident with F1 hinds rearing F2 calves having a lower BCS for the latter part of lactation. There was also a significant interaction between calf genotype, calf sex and time (P ¼0.048); F1 hinds rearing F2 male calves had a lower BCS (3.0) compared with F1 hinds rearing F2 female calves (BCS 3.4) during the latter part of lactation (days 165 to 234). F1 hinds rearing F2 female calves were not significantly different from red hinds in the study at this time.
Fig. 1. Profiles of mean live weight (a), body condition score (b) and udder score (c) for red deer hinds rearing red deer calves (solid triangles, dashed line) and F1 calves (solid circles, solid line) and red wapiti (F1) hinds rearing F2 calves (open circles, dotted line) during late pregnancy and lactation. Standard error bars (sed) are represented as vertical bars on each graph. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
The effect of calf genotype on hind udder score produced a significant interaction with time (P¼0.002). Hinds pregnant with F1 or F2 calves had significantly lower udder scores before calving (Fig. 1c) than hinds pregnant with a red calf, whereas post-calving, F1 hinds rearing F2 calves generally had lower, and red hinds rearing F1 calves higher, udder scores than red hinds rearing red calves for the remainder of lactation. Hind dry matter intake from pasture (Table 2) was not significantly different regardless of the size of hind or the genotype of the calf at any one measurement, but the average pasture intake was greatest in F1 hinds rearing F2 calves, intermediate in red deer hinds rearing F1 calves and lowest in red deer hinds rearing red deer calves (Table 2).
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Dry matter intake from pasture was approximately 6 kg DM/d during early lactation, falling to approximately 2 kg DM/d by day 197 of lactation. There was a trend (P¼0.053) towards a higher intake for F1 hinds rearing F2 calves than other hinds at day 76. Hinds were also supplemented with barley grain during the final intake measurement period (day 197) and estimates of grain intake from energy balance calculations indicated that the F1 hinds rearing F2 calves were consuming significantly more grain than red hinds rearing F1 calves or red calves (Table 2), resulting in higher total energy intakes at that time. Lower pasture digestibility was calculated for F1 hinds than red hinds (Table 2) and this led to no significant differences in pasture energy intake between hinds rearing calves of differing genotypes.
3.3. Calf live weight, live weight gain and milk intake While F2 calves were born significantly heavier (Table 3), the F1 calves were significantly heavier by day 76 and remained so for the rest of lactation, while red calves remained the lightest throughout (Table 3). Live weight gain of F1 calves was greatest throughout the lactation (Table 3). F2 calves had a similar live weight gain to F1 calves at the first measurement, but had slower growth rates thereafter, except at the last measurement in early winter. Red calves had the slowest growth rates throughout, though live weight was not significantly lower than F2 calves at days 51, 76 and 104 (Table 3). Female calves were born 1.4 kg lighter than male calves and remained lighter throughout the experiment (Table 4) being 12.1 kg lighter at day 197. The live weight gain of female calves was significantly slower than male calves (Table 4). There was no interaction between calf genotype and gender. Calf milk consumption (Fig. 2) was similar in F1 calves and F2 calves throughout the lactation, and significantly
greater than red calves on days 20 and 76 of lactation. At day 20 of lactation the gender of the calf had a significant effect with male calves consuming more milk (P ¼0.004; Table 4). Differences were no longer apparent for the rest of lactation. There was no interaction between calf genotype and gender for calf milk consumption. Total and pasture calf energy intakes were calculated (Fig. 3) and indicated that the F1 calves had the greatest pasture requirements to meet their calculated energy needs. The pasture requirement for the F2 calves was potentially lower than the other genotypes on days 51 and 76, but increased to be intermediate between the F1 and red deer calves thereafter. The variation in calf live weight (Fig. 4) was greatest in the F2 calves, intermediate in the F1 calves and lowest in
Table 3 Influence of calf genotype on calf live weight and live weight gain throughout lactation.
Calf age (d) Birth 20 51 76 104 197 Calf age (d) 20 51 76 104 197
Calf genotype Red F1
F2
P value
sed
Live weight (kg) 9.91 11.3 15.9 22.0 30.8 36.9 43.3 52.5 51.3 63.8 63.7 83 Live weight gain1
12.7 23.2 34.9 47.9 57.6 72.5 (g/d)
o0.001 o0.001 o0.001 0.001 0.001 o0.001
0.64 0.77 1.47 2.39 2.71 3.39
407 426 309 369 30
539 444 353 432 59
0.002 o0.001 0.002 o0.001 0.048
39 46 22 32 12
585 590 404 551 65
1 Live weight gain estimated by linear regression from liveweights recorded around each days of age point. This does not represent the live weight gain of the previous period.
Table 2 Feed dry matter and energy intake and pasture dry matter digestibility of hinds rearing red, F1 and F2 calves during lactation. Calf genotype Red Time after calving (d) 51 76 104 1971 Average Time after calving (d) 51 76 104 197 Time after calving (d) 51 76 104 197 1 2 3
Pasture intake (kg DM/d) 5.69 6.73 4.75 4.49 3.89 3.99 2 2.03 (0.27) 2.28 (0.41) 3.63 4.06 Pasture digestibility (g/100 g DM) 72.7 72.8 79.7 79.5 74.8 74.7 75.7 75.7 Total energy intake (MJME/d) 58.6 67.2 55.2 51.8 42.3 42.4 22.7 (19.9)3 26.0 (20.0)
Includes both pasture and grain supplement. Estimated grain supplement intake in brackets. Energy from pasture intake in brackets.
F2
F1
P value
Sed
0.227 0.053 0.102 0.001 0.039
0.62 0.47 0.57 0.10 0.33
70.0 76.4 65.6 70.7
0.067 0.010 0.005 o0.001
1.21 1.08 2.76 1.20
59.3 55.5 43.3 29.6 (20.0)
0.323 0.168 0.622 0.001
7.46 5.72 7.37 1.47
6.02 5.10 4.68 2.76 (0.79) 4.75
D.R. Stevens et al. / Livestock Science 170 (2014) 172–180
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Table 4 Influence of calf gender on calf live weight and calf live weight gain and calf milk intake during lactation. Gender Male Calf age (d) 20 51 76 104 197 Calf age (d) Birth
Female
P value
Hind milk production (kg/d) 3.67 3.15 0.004 3.61 3.14 0.159 2.50 2.46 0.70 1.66 1.60 0.76 0.59 0.58 0.91 Live weight (kg) 12.2 10.8 0.030 23.0 19.3 0.001
sed
0.13 0.33 0.22 0.23 0.10 0.59 0.57
20 37.8
31.2
0.001
1.09
54.1
46.0
0.001
2.18
64.6
55.5
0.001
2.47
82.6
70.5
0.001
3.10
51 76 104 197 Calf age (d)
Live weight gain (g/d) 606 480
o 0.001
29
20 552
448
0.008
34
381
351
0.141
20
496
445
0.09
29
80
41
0.002
11
51 76 104 197
Fig. 3. Mean calculated daily energy intakes of pasture (solid lines) and total feed (dotted lines) for red deer (solid triangles), F1 (solid circles) or F2 (open circles) calves. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
and 386 kg, respectively) producing more milk than hinds rearing red deer calves (325 kg; SED ¼24.2, P ¼0.024). There was no significant relationship between hind live weight and total lactation output, even when genotype was added as a grouping factor (Fig. 5). When average calf live weight was compared with hind milk output (Fig. 6) then a significant interaction between genotypes was apparent. There was a positive linear relationship between average calf live weight and hind milk production for both red hinds rearing red calves (P ¼0.072) and F1 hinds rearing F2 calves (P¼0.008). Approximately 14.6 kg more milk was produced for each extra kg of average calf liveweight at weaning. However, calf live weight had no significant effect on hind lactation output when red deer hinds were rearing F1 calves (P¼0.439). 4. Discussion
Fig. 2. Mean daily milk production of red deer rearing a red calf (solid triangle, dashed line) or an F1 calf (solid circle, solid line), or an F1 hind rearing an F2 calf (open circles, dotted line) during lactation. Standard error bars (sed) are represented as vertical lines at each measurement date. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the red deer calves when measured at birth (Fig. 4a), day 104 (Fig. 4b) and day 197 (Fig. 4c). 3.4. Total hind lactation output Calf genotype had a significant influence on total lactation output with hinds rearing F1 and F2 calves (393
The results need to be considered in two ways. The first is to compare the milk output of red hinds rearing red calves to that of F1 hinds rearing F2 calves: i.e. when hinds of disparate live weight rear calves of similar genotype to themselves. The second is to compare those outputs with that achieved by red hinds rearing an F1 calf. F1 hinds rearing F2 calves weighed more and produced more milk than red hinds rearing red calves. Carrion et al. (2008) reported daily milk production of Iberian red deer (C.e. hispanicus) hinds to be 18.7 mL/kg LW when accounting for other influences such as day of lactation. In the present study F1 hinds were, on average, 58.7 kg heavier than red hinds, and therefore had the potential to produce an extra 1.1 L milk/d above that of red hinds based on the data of Carrion et al. (2008). Landete-Castillejos et al. (2009) reported a total lactation yield of 2 L milk for each kg of hind live weight. Using that value, F1 hinds from the present study would be expected to produce an extra 117 L of milk during the course of the 126 d lactation reported, or approximately 0.6 L more milk/d, than that produced by red hinds rearing red calves. Indeed, the F1 hinds produced an average of 0.59 L more milk/d than red hinds to day 104
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Fig. 5. Hind live weight compared with milk production for red deer rearing a red calf (solid triangle) or an F1 calf (solid circle), or an F1 hind rearing an F2 calf (open circles) during lactation. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. Impacts of different calf genotypes on variability of calf liveweight (a) at birth and (b) at 104 days and (c) at 197 days of lactation. The box spans the interquartile range of the values in each variate, so that the middle 50% of the data lie within the box, with the line within the box indicating the median. Whiskers extend beyond the ends of the box as far as the minimum and maximum values.
and an extra 0.49 L milk/d on average over the experimental period of 197 days, though our hypothesis that greater calf demand determines milk production would also support this increase. Peak lactation yield, as calculated from NRC (2006) using the relationship by Oftendal (1984) where (NEL¼ 435 kJ BW0.70), suggests that the red deer hinds in this study had a theoretical peak lactation output of approximately 12 MJ/d, while the F1 hinds had a potential peak lactation output of approximately 16 MJ/d. These translate into milk yields of 2 and 2.6 kg/d. However, in this study, the milk output of red hinds rearing a red calf was
Fig. 6. Average calf live weight compared with the full season milk output of red deer hinds rearing red calves (solid triangle, dashed regression line; y¼11.55x 170, r2 ¼0.823) or F1 calves (solid circle, solid regression line; y¼ 550–3.26x, r2 ¼ 0.079), or F1 hinds rearing F2 calves (open circles, dotted regression line; y¼ 11.18x 145, r2 ¼ 0.615) during lactation.
approximately 2.9 kg/d, a red hind rearing an F1 calf was 3.7 kg/d and an F1 hind rearing an F2 calf was 3.9 kg/d. This suggests lactation outputs of 660 kJ/kg BW0.70 for red hinds rearing a red calf and F1 hinds rearing an F2 calf, but 800 kJ/kg BW0.70 for red hinds rearing an F1 calf. Results from Archer et al. (2013) indicated similar values of 653 and 854 kJ/kg BW0.70 produced by red hinds rearing red and F1 calves, respectively. It could be that calf demand, rather than hind live weight, is the main driver of hind milk production. This hypothesis is supported by red hinds rearing an F1 calf in this study having the same milk production as much larger F1 hinds rearing an F2 calf, demonstrating that calf demand has an important influence on milk production. However, the hind may be primed to provide the extra milk through in utero signals from the F1 calf. Evidence for this comes from the research of (Moore, 1966) who showed that ewe
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milk production is influenced by lamb genotype and suckling vigour and frequency. Cross fostering of Corriedale lambs to Merino ewes saw an increase in milk production over the same genotype suckling Merino lambs. Also, the increased suckling stimulus of twin lambs is the major reason for increased ewe milk production, which averages 41% more in twin bearing than single bearing ewes (Treacher, 1983). In the present study the udder score of red hinds rearing F1 calves was significantly greater than that of F1 hinds rearing F2 calves during peak lactation, indicating that a greater store of milk was being generated in response to higher demand. Although suckling observations in a previous study suggest that suckling frequency is unaffected by calf genotype, this may have been compensated for by larger calves sucking more vigorously (Ward et al., 2007). Udder score of the red hinds rearing an F1 calf indicated that a larger storage capacity may be available when required. However, the storage capacity of both red and F1 hinds rearing calves of like genotype appeared similar as represented by udder score, supporting the concept that much of the milk provided during a ‘normal’ lactation is produced on demand as suckling occurs. The evidence points to demand driving lactation when hind-calf genotype is the same, but pre-natal influences on mammogenesis cannot be ruled out when attempting to explain the response of the red hind rearing an F1 calf. However, pre-natal udder scores appeared to be related to potential birth date rather than indicating enhanced mammogenesis in red hinds carrying F1 calves as the pre-calving udder score of red and F1 hinds carrying crossbred calves with similarly late birth dates was similar and lower than red hinds carrying red calves with an earlier birth date. Differences in udder score were only noted post-parturition and reflected increased cistern capacity as the scoring system specifically relates to state of engorgement, although no definitive measurement of udder dimension was made. Data for F2 calves were more variable and provided a significant insight to what might be driving lactation as the hind live weights were much greater than those of the red dams. This is a really important point regarding the outcomes, as mean milk production increased by 14.6 kg/kg mean calf live weight over the 197 day lactation (R2 ¼0.50). Variability in F2 progeny is a common feature in crossbreeding programmes (Sorensen et al., 2008). Heterosis is greatest in the F1 and declines in the F2. Several studies in cattle suggest that the impacts of heterosis on milk yield are relatively low at between 2 and 8%, (Sorensen et al., 2008). Further, the impact of maternal heterosis on weaning weight is low in both cattle (Demeke et al., 2003; Kahi et al., 2000) and sheep (Geenty, 1979; Gootwine and Goot, 1996). Recombination effects are often negative (Sorensen et al., 2008) and may have influenced the performance of the F2 generation recorded in this experiment. The size of the relative effects of heterosis can be influenced by the type of cross breeding. In cattle of different species, Theunissen et al. (2013) reported that maternal heterosis was high in Bos taurus sanga progeny but not in Bos indicus sanga progeny, while the opposite was seen in individual heterosis. This may suggest that where relatively
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little selection pressure has been applied then a high degree of heterozygosity may already be present in the population, limiting the opportunity for heterosis. While the F1 and F2 calves did grow faster than the red calves, as predicted, the milk production of the hinds was relatively similar. The recombination of genes in the F2 calf appears to have resulted in high levels of phenotypic variation of F2 progeny with calf live weights ranging from the lowest to the highest average live weights recorded. However, the milk yield from red hinds rearing F1 calves was not related to calf live weight and indicated that milk production from the hind had reached a maximum at approximately 400 L milk over the 197 d lactation, and importantly, regardless of the size of the calf, following similar trends to other observations of milk yield from crossbred dams (Sorensen et al., 2008). This concept of approaching maximum milk output over the course of lactation when a red hind rears an F1 calf is supported by the lower BCS of those hinds compared to red hinds rearing red calves in early lactation. Red hinds rearing red calves and F1 hinds rearing F2 calves appeared to lose less BCS during early to peak lactation than those red hinds rearing an F1 calf. Use of body reserves to achieve the extra milk production may have been necessary to offset an inability to eat more feed to meet the extra energy requirement. This is a similar result to Archer et al. (2013) where extra energy requirement for lactation came from body reserves rather than feed intake, suggesting that under ‘normal’ conditions where the hind and the calf are of the same genotype then milk production is supported by feed intake unless feeding conditions are poor, as presented by Landete Castillejos et al. (2003). A decline in BCS was noted at approximately 120 days after calving in all hinds. While the red hinds recovered some of that loss, F1 hinds did not. However, milk production was relatively low at this point and the decline in production was similar for all hinds suggesting that this loss of condition at that time had little effect on total milk production. The F1 calf had a higher energy demand and greater growth rate than either the red or F2 calf. Both the red and F2 calves appeared to be behaving relatively similarly with respect to pasture intake. However, the F1 calves had a higher pasture energy intake to meet the greater demand. There was no evidence from Archer et al. (2013) that the F1 calf had greater feed conversion efficiency than the red calf, so the assumption that the F1 calf had a greater appetite for pasture due to a greater drive to grow is intuitive. Archer et al. (2013) found no significant difference between the pasture intakes of red or F1 calves, and assigned the difference in growth rate to the difference in milk intake. One potential reason for the difference between this experiment and that of Archer et al. (2013) is the higher milk intakes recorded in F1 calves in that study. These were approximately 0.4 L/d greater than those measured in this experiment, and may have been related to the larger hinds in that study. The use of F2 calves being suckled by F1 hinds provided a unique insight into the role of the calf in determining milk production in the hind, as this combination provided a significantly wide range of calf live weights that spanned
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those of the red and F1 calves to which they were compared, while providing hinds of much larger live weights. The evidence gathered using this approach, and the previous experiment by Archer et al. (2013), suggests that the generally held consensus that hind lactation output is driven by hind live weight may need modified. It appears that calf demand also plays a major part in driving lactation output from the hind. The hind then moderates the actual outcome depending on her ability to reach maximal milk output, which was achieved in this experiment with red wapiti calves suckling red deer hinds. Conflict of interest statement There are no conflicts of interest associated with the publication of this paper. Acknowledgements We are grateful to Lynne Rhodes for provision of AI services, and to Bruce Sinclair for analysis of deuterium content. This work was funded by the New Zealand Foundation of Research, Science and Technology (Contract C10 0709) and DEEResearch Ltd. References ARC, 1980. The Nutrient Requirements of Ruminant Livestock. Agricultural Research Council, Farnham Royal. Archer, J.A., Asher, G.W., Stevens, D.R., Ward, J.F., Scott, I.C., O’Neill, K.T., Littlejohn, R.P., Barrell, G.K., 2013. Influence of calf genotype on dam lactation and calf growth in farmed red deer (Cervus elaphus). Livest. Sci. 157, 289–298. Asher, G.W., Veldhuizen, F.A., Morrow, C.J., Duganzich, D.M., 1994. Effects of exogenous melatonin on prolactin secretion, lactogenesis and reproductive seasonality of adult female red deer (Cervus elaphus). J. Reprod. Fertil. 100, 11–19. Audige, L., Wilson, P.R., Morris, R.S., 1998. A body condition score system and its use for farmed red deer hinds. N.Z. J. Agric. Res. 41, 545–553. Blaxter, K.L., 1952. The nutrition of the young Ayrshire calf. 6. The utilisation of energy of whole milk. Br. J. Nutr. 16, 199–212. Carrion, D., Garcia, A.J., Gaspar-Lopez, E., Landete-Castillejos, T., Gallego, L., 2008. Development of body condition in hinds of Iberian red deer during gestation and its effects on calf birth weight and milk production. J. Exp. Zool. A: Ecol. Genet. Physiol. 309, 1–10. Demeke, S., Neser, F.W.C., Schoeman, S.J., 2003. Early growth performance of Bos taurus Bos indicus cattle crosses in Ethiopia: estimation of individual crossbreeding effects. J. Anim. Breed. Genet. 120, 245–257. Dove, H., 1988. Estimation of the intake of milk by lambs from the turnover of deuterium or tritium-labelled water. Br. J. Nutr. 60, 375–388. Dove, H., Freer, M., 1979. The accuracy of tritium labeled water turnover rate as an estimate of milk intake in lambs. Aust. J. Agric. Res. 30, 725–740.
Dove, H., Mayes, R.W., 1991. The use of plant wax alkanes as marker substances in studies of the nutrition of herbivores: a review. Aust. J. Agric. Res. 42, 913–952. Dove, H., Mayes, R.W., 1996. Plant wax components: a new approach to estimating intake and diet composition in herbivores. J. Nutr. 126, 13–26. Geenty, K.G., 1979. Lactation performance, growth, and carcass composition of sheep. N.Z. J. Agric. Res. 22, 241–250. Gootwine, E., Goot, H., 1996. Lamb and milk production of Awassi and East-Friesian sheep and their crosses under Mediterranean environment. Small Ruminant Res. 20, 255–260. Kahi, A.K., Thorpe, W., Nitter, G., Baker, R.L., 2000. Crossbreeding for dairy production in the lowland tropics of Kenya: I. Estimation of individual crossbreeding effects on milk production and reproductive traits and on cow liveweight. Livest. Prod. Sci. 63, 39–54. Landete-Castillejos, T., Garcia, A., Carrion, D., Estevez, J.A., Ceacero, F., Gaspar-Lopez, E., Gallego, L., 2009. Age-related body weight constraints on prenatal and milk provisioning in Iberian red deer (Cervus elaphus hispanicus) affect allocation of maternal resources. Theriogenology 71, 400–407. Landete-Castillejos, T., Garcia, A., Garde, J., Gallego, L., 2000. Milk intake and production curves and allosuckling in captive Iberian red deer, Cervus elaphus hispanicus. Anim. Behav. 60, 679–687. Landete Castillejos, T., Molina, P., Garcia, A., Gomez, J.A., Gallego, L., 2003. Estimate and production of milk energy in two subspecies of red deer: Cervus elaphus hispanicus and C.e. scoticus. J. Exp. Zool. 300A, 152–157. Mayes, R.W., Lamb, C.S., Colgrove, P.M., 1986. The use of dosed and herbage n-alkanes as markers for the determination of herbage intake. J. Agric. Sci. 107, 161–170. Moore, R.W., 1966. Effects of genotype of ewe and lamb on milk production. Aust. J. Agric. Res. 17, 191–200. NRC, 2006. Nutrient Requirements of Small Ruminants: Sheep, Goats, Cervids and New World Camelids. National Research Council, Washington DC. Oftendal, O.T., 1984. Milk composition, milk yield and energy output at peak lactation: a comparative review. Symp. Zool. Soc. London 51, 33–85. Pearse, A.J., 1992. Farming of wapiti and wapiti hybrids in New Zealand, The biology of deer. In: Proceedings of the International Symposium on the Biology of Deer, 28 May–1 June 1990, Mississippi State University, USA. Springer-Verlag, New York, USA: 1992. 173-177. Pearse, A.J., Fung, L., 2007. The deer industry’s productivity strategy: a five year vision. In: Proceedings of the New Zealand Society of Animal Production 67, 73-77. Rhodes, L., Pearse, A.J., Asher, G.W., 2003. Approaches in developing a successful trans-cervical AI programme for farmed deer. In: Proceedings of the New Zealand Society of Animal Production 63, 258-261. Sorensen, M.K., Norberg, E., Pedersen, J., Christensen, L.G., 2008. Invited review: Crossbreeding in dairy cattle: a Danish perspective. J. Dairy Sci. 91, 4116–4128. Stevens, D.R., Corson, I.D., 2003. Optimising calf growth of red deer in summer and autumn. In: Proceedings of the New Zealand Society of Animal Production 63, 218-221. Theunissen, A., Scholtz, M.M., Neser, F.W.C., MacNeil, M.D., 2013. Crossbreeding to increase beef production: additive and non-additive effects on weight traits. S. Afr. J. Anim. Sci. 43, 143–152. Treacher, T.T., 1983. Nutrient requirements for lactation in the ewe. In: Haresign, W. (Ed.), Sheep Production, Butterworths, London, pp. 133–153. Ward, J.F., Archer, J.A., O’Neill, K.T., Littlejohn, R.P., 2007. Comparison of suckling frequency of red and F1 wapiti-red calves reared on red hinds. In: Proceedings of the New Zealand Society of Animal Production 67, 237-241.
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Hind genotype influences on lactation and calf growth in farmed red deer (Cervus elaphus) D.R. Stevens a,n, J.A. Archer a, G.W. Asher a, J.F. Ward a, I.C. Scott a, K.T. O’Neill a, R.P. Littlejohn a, G.K. Barrell b a b
AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand Lincoln University, Agriculture and Life Sciences Division, PO Box 84, Canterbury 8150, New Zealand
a r t i c l e in f o
abstract
Article history: Received 18 May 2014 Received in revised form 17 September 2014 Accepted 20 September 2014
Multiparous red deer (Cervus elaphus scoticus) hinds (n ¼ 18) were artificially inseminated with semen from a red deer stag (n ¼8) or wapiti bull (C.e. nelsoni) (n ¼ 10) to produce red deer or F1 crossbred (C.e. scoticus C.e. nelsoni) calves. A further seven wapiti red deer (F1) hinds were artificially inseminated with semen from an unrelated F1 stag to test the hypotheses that (1) crossbred hinds rearing crossbred calves will produce more milk to support calf growth than red deer hinds rearing crossbred calves, and (2) the extra lactation demand of crossbred calves will exert a more detrimental effect on red deer hind live weight and body condition than would occur if the dam was a crossbred hind. Hinds and calves were grazed on ryegrass and white clover pastures and supplemented with pasture silage and barley grain when pasture supply was inadequate. Calves were left with their mothers until approximately 240 days of age. Mean body condition score (BCS) was lower in F1 hinds rearing F2 calves during late lactation (days 150 to 240, P o 0.05) than red deer hinds rearing either red deer or F1 calves. F1 calves grew significantly faster than red deer calves and were heavier at all ages, while F2 calves were intermediate. Milk intake of both F1 and F2 calves was higher than red deer calves until day 76 of lactation (P 4 0.05), but similar thereafter. Male calves had a higher milk intake than female calves at 20 days of age only (P ¼ 0.004). The average hind pasture intake was greatest in F1 hinds rearing F2 calves, intermediate in red deer hinds rearing F1 calves and lowest in red deer hinds rearing red deer calves (P ¼ 0.038). Total milk output for the lactation increased by approximately 14.6 kg/kg average calf live weight at weaning for both F1 hinds rearing F2 calves (P ¼ 0.008) and red deer hinds rearing red deer calves (P¼ 0.072), suggesting that calf demand rather than hind liveweight was the key determinant of lactation performance. This was not the case for red deer hinds rearing F1 calves suggesting that there is an upper limit to lactation output depending on hind size. These results do not support the hypothesis that a crossbred hind rearing a crossbred calf will produce more milk than a red deer hind rearing a crossbred calf and provides evidence that the milk production of the hind is primarily driven by milk demand of the calf but has an upper limit depending on the size of the hind. The second hypothesis was not supported as F1 hinds rearing F2 calves exhibited greater loss of body condition score relative to the red deer hinds rearing either red deer or F1 calves in this study. This suggests that the additional energetic demands on a hind from feeding an F1 calf may be met with adequate nutrition. & 2014 Elsevier B.V. All rights reserved.
Keywords: Red deer Crossbreds Lactation Intake Growth
n
Corresponding author. Tel.: þ64 3 4899035. E-mail address: [email protected] (D.R. Stevens).
http://dx.doi.org/10.1016/j.livsci.2014.09.019 1871-1413/& 2014 Elsevier B.V. All rights reserved.
D.R. Stevens et al. / Livestock Science 170 (2014) 172–180
1. Introduction Venison production systems in New Zealand generally aim to produce red deer stags for slaughter in their first year of life to meet the premium chilled venison markets in Europe during the period of traditional venison consumption (Pearse and Fung, 2007). Achieving this requires fast growing animals to meet specified carcass weights by 7–11 months of age. The period of greatest differential between average and potential stag growth performance on New Zealand deer farms occurs during the first six months of the deer’s life. This coincides with the suckling period, indicating that lactation performance of hinds contributes significantly to production (Stevens and Corson, 2003). Accordingly, it is of interest to better understand the drivers of calf growth over this period, including factors influencing lactation. One major driver of calf growth potential is genotype. In New Zealand deer farming, a terminal-sire system is commonly practiced, using stags with a high content of wapiti genes (red deer subspecies of North American origin Cervus elaphus manitobensis, nelsoni, roosevelti) to mate New Zealand red hinds (NZ red) of English and Scottish origins (Cervus elaphus scoticus). The resulting crossbred calves have higher growth rates than calves sired by red deer stags (Pearse, 1992), and so overall productive outputs are considerably higher. However, the mechanisms which support these higher growth rates are poorly understood. What is the major driver of calf growth during lactation—calf demand for milk, or milk supply? In a previous paper (Archer et al., 2013) the impact of calf genotype on the lactation output from hinds of a single genotype (C.e. scoticus) was described. That experiment investigated the question of whether hind lactation is influenced by calf genotype and concluded that red deer hinds rearing crossbred calves produced more milk than red deer hinds rearing red deer calves. This paper addresses the opposite effect of calf genotype—what is the effect of dam genotype on lactation output? How much milk will a crossbred hind produce when raising a crossbred calf, compared with a red deer hind raising a crossbred calf? Does the importance of calf milk demand vs. hind milk supply change over the course of lactation as the calf becomes less dependent on milk? What is the balance of the calf’s diet of milk and pasture and how does this change over the lactation period? What are the implications for hinds of different genotypes
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rearing a calf of a similar genotype in terms of live weight and body condition? The contrast in growth potential of wapiti-cross and red deer calf genotypes offers a useful model to better understand the drivers of lactation performance in deer. Moreover a similar contrast in maternal genotype may provide additional insight to these factors. This paper reports on studies conducted using this model to quantify lactation outputs in deer farmed in New Zealand and relate this to calf growth and impacts on the hind. The hypotheses tested are as follows: (1) Crossbred hinds rearing crossbred calves will produce more milk to support calf growth than red deer hinds rearing crossbred calves. (2) The extra lactation demand of crossbred calves will exert a more detrimental impact on red deer hind live weight and body condition than would occur if the dam was a crossbred hind.
2. Materials and methods 2.1. Animals and management The study was conducted on a cohort of calves born at the Invermay Agricultural Centre (Mosgiel, New Zealand) in November/December 2004. All experimental procedures had prior approval from the Invermay Animal Ethics committee. A total of 18 multiparous red deer hinds of “New Zealand red deer” breeding (predominantly derived from C.e. scoticus) produced calves from artificial insemination with semen from a single red deer (n¼ 8) or wapiti (C.e. nelsoni) sire (n ¼10). In addition, a further seven wapiti red deer (F1) hinds produced calves from insemination with semen from an unrelated wapiti red deer (F1) stag to generate calves with 50% wapiti parentage (F2); i.e. hinds with 50% wapiti parentage rearing calves with 50% wapiti parentage.. Artificial insemination was performed following oestrous synchronisation according to the procedures described by Rhodes et al. (2003). All hinds raised calves the previous season. Table 1 contains a summary of the hind and calf genotype combinations which were used in subsequent experimentation. Calves were born from 21 November to 7 December. Hinds and calves were grazed on predominantly ryegrass (Lolium perenne) pastures and were supplemented
Table 1 Experimental design, calving date, calf birth weight, post-calving hind live weight (LW) and hind LW change in late lactation (day 75 to day 200 after mean calving date). Treatment Hind genotype Sire genotype Calf genotype n Mean birth date (range) Mean gestation length (d) Mean calf birth weight (kg) Mean hind live weight (kg) Hind LW change late lactation (kg)
NZ red NZ red NZ red 8 26 Nov ( 71.35) 232 (7 1.35) 9.9 ( 7 0.24) 111.7 ( 7 2.7) 3.4 ( 7 2.9)
NZ red Wapiti F1 10 3 Dec ( 71.21) 239 ( 71.21) 11.3(7 0.40) 117.3 ( 72.9) 2.1 ( 7 2.8)
NZ red Wapiti NZ red Wapiti F2 7 2 Dec ( 7 1.42) 238 ( 7 1.42) 12.7( 70.78) 170.4 ( 72.6) 9.4 ( 73.0)
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with pasture silage and barley grain (approximately 0.5 kg grain/head/d) when pasture supply was inadequate during winter. Hinds were checked daily during the calving period and birth date, birth weight of calves and calfdam matches were recorded. Calves were weaned in late May 2005 to match the practice of “post-rut weaning” which is used by a significant proportion of New Zealand deer farmers. 2.2. Measurements Live weights of hinds were recorded from 28 October during pregnancy at approximately 2 weekly intervals until the end of the experiment on 30 May 2005. At each weighing an udder score (US) on a 0–5 scale (after Asher et al., 1994) was recorded, where 0 equates to no palpable mammary development and 5 represents a fully engorged udder. Hinds were also assessed for body condition score (BCS) (Audige et al., 1998), with a score of 1 representing an emaciated animal and 5 representing an obese animal. Calves were weighed at birth, and then at approximately 2 week intervals throughout lactation. Measurements of milk intake by the calves and pasture intake by the hinds were made on 16 December, 7 January, 3 February, 3 March and 25 May following the protocols outlined by Archer et al. (2013). Briefly, milk intake measurements were conducted using the double isotope dilution technique (Dove, 1988) over a five day period. Concentrations of tritium and deuterium isotopes were analysed in serum of hinds and calves taking account of the growth of the body water pool of the calf (Dove and Freer, 1979) and for the concentration of deuterium in water entering the body water pool of calves from the outside environment. Analysis of dry matter content of milk was performed on milk samples after thawing and homogenising. Milk samples were weighed and then dried by freeze-dry lyophilisation for 48 h. Remaining solids content was reweighed and the results used to calculate the solids content of individual milk samples. Solids content and milk water intake (from calculations described above) were then used to calculate total milk intake (water plus solids) corrected to 22% solids (representing the approximate average DM of samples obtained). 2.3. Hind and calf pasture intake measurements Pasture intake was calculated using the C32-alkane dilution method (Dove and Mayes, 1996). Hinds were orally dosed daily for 7 consecutive days with 100 mg of n-dotriacontane (C32) powder (Nufarm Health and Sciences NZ, Auckland, NZ) suspended in 5 mL of food grade canola oil on four occasions during lactation with the first collection on 20 and 21 January, being 51 days after mean calving date. The initiation of each treatment period coincided with the final day (Day 5) of each milk measurement period. After the final daily dosing and on the following day 40 g of faecal sample was collected directly from the rectum of each animal. Faecal samples were frozen at 20 1C and later freeze dried and ground for analysis. A plucked sample of pasture, representative of
that eaten was also collected at this time, frozen and then later freeze dried. Analysis for C31, C32, C33, and C35 alkane concentrations was undertaken by the Department of Animal and Veterinary Science analytical laboratory, Lincoln University, using the technique of Mayes et al. (1986), with the modification that samples were digested in an oven at 90 1C instead of on a heating block. Intake was calculated by the alkane dilution in faeces (Dove and Mayes, 1991), as the mean of that calculated from C31:C32 and C33:C32 ratios. Apparent dry matter digestibility was also calculated (Dove and Mayes, 1991) (Digestibility¼ 1 (herbage alkane concentration/faeces alkane concentration) as the mean value of the value calculated using C33 and C35). 2.4. Calculated energy intakes Gross energy intake of calves from milk was calculated by applying a factor of 6.125 MJ per kg of milk intake adjusted to 22% DM. This factor was obtained by applying the energy content equation of (Landete Castillejos et al., 2003) to the milk composition parameters at week 2 of lactation (Landete Castillejos et al., 2000). The gross energy intake was converted to a metabolisable energy intake by multiplying by a factor of 0.95 (Blaxter, 1952). Energy intake of calves and hinds from pasture was calculated from the digestibility of the diet (ME (MJ)¼ 18.4 DMD 0.81; (ARC, 1980)). The energy requirements of both hinds and calves was calculated using the following derived equations (NRC, 2006). Hind energy requirement ¼ 0:544BW0:75 þ ðMilk energy 0:65Þ Adjustments were made for live weight gain (LWG) or live weight loss (LWL) (NRC, 2006). Additional requirement for gain ¼ LWGðkgÞ:54:8 MJME=kg Reduction in requirement for loss ¼ LWL ðkgÞ 18MJME=kg Calf requirements were calculated using a coefficient for maintenance (Archer et al., 2013) from a previous experiment using similar red deer genotypes, and a coefficient for gain (NRC, 2006). Calf energy requirement ¼ 0:741:BW0:75 þgain ðkgÞ 22:3MJME
2.5. Statistical analysis Milk intake, milk solids, feed intake and water turn over (hind and calf) data were analysed in two ways. First, data at each sample time were analysed using the general linear model, fitting calf birth date as a covariate and then adding calf breed and calf sex as fixed effects. Calf birth date was only significant as a covariate for the first two periods and so was dropped from the model thereafter. Secondly, data for all times were analysed by residual maximum likelihood (REML), fitting calf birth date as a covariate, date (as a continuous variable), and calf breed
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and the interaction of calf breed and date, with a term for date. This method was also repeated using calf age in place of date, but this gave no additional insights. Data (apart from live weight, BCS and US) is reported to correspond to the final date of each milk measurement, being days 20, 51, 76, 104, and 197 of age using the mean calving date of 30 November. Calf live weight gain was calculated to represent each intake measurement period by applying linear regression to the live weights that were collected around the time of measurement. Values presented for calf data from the first two periods are adjusted for birth date. Total lactation output from the hinds was calculated by multiplying the number of days between each measurement date by the arithmetic mean of the measurements made at each date. So, for example, the number of days in the first period (20 days) was multiplied by the mean of Day 0 (start of lactation) and the measured milk yield at day 20 to calculate the milk production for that period. Linear regression was used to compare milk yield to post-calving hind live weight and to the average calf live weight (as the arithmetic mean, weighted for the days in each period) applying calf genotype as a grouping factor. 3. Results 3.1. General A summary of the experimental design and key statistics of birth dates and hind live weights is given in Table 1. F1 and F2 calves were associated with longer gestation lengths and, hence, later birth dates than for red deer calves, and were also heavier at birth (Table 1). Milk dry matter concentration averaged 22.8, 22.2 and 22.2 g DM/100 g (sed ¼0.89 g DM/100 g) from hinds rearing red, F1 and F2 calves respectively. Milk dry matter concentration increased during the lactation being 21.1, 21.6, 21.6, 23.7 and 24.1 g DM/100 g (sed ¼0.85 g DM/ 100 g) at days 20, 51, 76, 104 and 197, respectively. The gender of the calf did not influence milk solids concentration. The milk solids concentration from red hinds and the larger red wapiti hinds was similar throughout. 3.2. Hind live weight, BCS, US and intake Mean hind live weight was much higher for F1 hinds rearing F2 calves than for the other genotypes (P o0.001; Fig. 1a), and declined somewhat more for this group during late lactation (Po0.05; Table 1). Mean hind BCS values are presented in Fig. 1b. There was no main effect of calf genotype on hind BCS, but a significant interaction between calf genotype and time was evident with F1 hinds rearing F2 calves having a lower BCS for the latter part of lactation. There was also a significant interaction between calf genotype, calf sex and time (P ¼0.048); F1 hinds rearing F2 male calves had a lower BCS (3.0) compared with F1 hinds rearing F2 female calves (BCS 3.4) during the latter part of lactation (days 165 to 234). F1 hinds rearing F2 female calves were not significantly different from red hinds in the study at this time.
Fig. 1. Profiles of mean live weight (a), body condition score (b) and udder score (c) for red deer hinds rearing red deer calves (solid triangles, dashed line) and F1 calves (solid circles, solid line) and red wapiti (F1) hinds rearing F2 calves (open circles, dotted line) during late pregnancy and lactation. Standard error bars (sed) are represented as vertical bars on each graph. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
The effect of calf genotype on hind udder score produced a significant interaction with time (P¼0.002). Hinds pregnant with F1 or F2 calves had significantly lower udder scores before calving (Fig. 1c) than hinds pregnant with a red calf, whereas post-calving, F1 hinds rearing F2 calves generally had lower, and red hinds rearing F1 calves higher, udder scores than red hinds rearing red calves for the remainder of lactation. Hind dry matter intake from pasture (Table 2) was not significantly different regardless of the size of hind or the genotype of the calf at any one measurement, but the average pasture intake was greatest in F1 hinds rearing F2 calves, intermediate in red deer hinds rearing F1 calves and lowest in red deer hinds rearing red deer calves (Table 2).
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Dry matter intake from pasture was approximately 6 kg DM/d during early lactation, falling to approximately 2 kg DM/d by day 197 of lactation. There was a trend (P¼0.053) towards a higher intake for F1 hinds rearing F2 calves than other hinds at day 76. Hinds were also supplemented with barley grain during the final intake measurement period (day 197) and estimates of grain intake from energy balance calculations indicated that the F1 hinds rearing F2 calves were consuming significantly more grain than red hinds rearing F1 calves or red calves (Table 2), resulting in higher total energy intakes at that time. Lower pasture digestibility was calculated for F1 hinds than red hinds (Table 2) and this led to no significant differences in pasture energy intake between hinds rearing calves of differing genotypes.
3.3. Calf live weight, live weight gain and milk intake While F2 calves were born significantly heavier (Table 3), the F1 calves were significantly heavier by day 76 and remained so for the rest of lactation, while red calves remained the lightest throughout (Table 3). Live weight gain of F1 calves was greatest throughout the lactation (Table 3). F2 calves had a similar live weight gain to F1 calves at the first measurement, but had slower growth rates thereafter, except at the last measurement in early winter. Red calves had the slowest growth rates throughout, though live weight was not significantly lower than F2 calves at days 51, 76 and 104 (Table 3). Female calves were born 1.4 kg lighter than male calves and remained lighter throughout the experiment (Table 4) being 12.1 kg lighter at day 197. The live weight gain of female calves was significantly slower than male calves (Table 4). There was no interaction between calf genotype and gender. Calf milk consumption (Fig. 2) was similar in F1 calves and F2 calves throughout the lactation, and significantly
greater than red calves on days 20 and 76 of lactation. At day 20 of lactation the gender of the calf had a significant effect with male calves consuming more milk (P ¼0.004; Table 4). Differences were no longer apparent for the rest of lactation. There was no interaction between calf genotype and gender for calf milk consumption. Total and pasture calf energy intakes were calculated (Fig. 3) and indicated that the F1 calves had the greatest pasture requirements to meet their calculated energy needs. The pasture requirement for the F2 calves was potentially lower than the other genotypes on days 51 and 76, but increased to be intermediate between the F1 and red deer calves thereafter. The variation in calf live weight (Fig. 4) was greatest in the F2 calves, intermediate in the F1 calves and lowest in
Table 3 Influence of calf genotype on calf live weight and live weight gain throughout lactation.
Calf age (d) Birth 20 51 76 104 197 Calf age (d) 20 51 76 104 197
Calf genotype Red F1
F2
P value
sed
Live weight (kg) 9.91 11.3 15.9 22.0 30.8 36.9 43.3 52.5 51.3 63.8 63.7 83 Live weight gain1
12.7 23.2 34.9 47.9 57.6 72.5 (g/d)
o0.001 o0.001 o0.001 0.001 0.001 o0.001
0.64 0.77 1.47 2.39 2.71 3.39
407 426 309 369 30
539 444 353 432 59
0.002 o0.001 0.002 o0.001 0.048
39 46 22 32 12
585 590 404 551 65
1 Live weight gain estimated by linear regression from liveweights recorded around each days of age point. This does not represent the live weight gain of the previous period.
Table 2 Feed dry matter and energy intake and pasture dry matter digestibility of hinds rearing red, F1 and F2 calves during lactation. Calf genotype Red Time after calving (d) 51 76 104 1971 Average Time after calving (d) 51 76 104 197 Time after calving (d) 51 76 104 197 1 2 3
Pasture intake (kg DM/d) 5.69 6.73 4.75 4.49 3.89 3.99 2 2.03 (0.27) 2.28 (0.41) 3.63 4.06 Pasture digestibility (g/100 g DM) 72.7 72.8 79.7 79.5 74.8 74.7 75.7 75.7 Total energy intake (MJME/d) 58.6 67.2 55.2 51.8 42.3 42.4 22.7 (19.9)3 26.0 (20.0)
Includes both pasture and grain supplement. Estimated grain supplement intake in brackets. Energy from pasture intake in brackets.
F2
F1
P value
Sed
0.227 0.053 0.102 0.001 0.039
0.62 0.47 0.57 0.10 0.33
70.0 76.4 65.6 70.7
0.067 0.010 0.005 o0.001
1.21 1.08 2.76 1.20
59.3 55.5 43.3 29.6 (20.0)
0.323 0.168 0.622 0.001
7.46 5.72 7.37 1.47
6.02 5.10 4.68 2.76 (0.79) 4.75
D.R. Stevens et al. / Livestock Science 170 (2014) 172–180
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Table 4 Influence of calf gender on calf live weight and calf live weight gain and calf milk intake during lactation. Gender Male Calf age (d) 20 51 76 104 197 Calf age (d) Birth
Female
P value
Hind milk production (kg/d) 3.67 3.15 0.004 3.61 3.14 0.159 2.50 2.46 0.70 1.66 1.60 0.76 0.59 0.58 0.91 Live weight (kg) 12.2 10.8 0.030 23.0 19.3 0.001
sed
0.13 0.33 0.22 0.23 0.10 0.59 0.57
20 37.8
31.2
0.001
1.09
54.1
46.0
0.001
2.18
64.6
55.5
0.001
2.47
82.6
70.5
0.001
3.10
51 76 104 197 Calf age (d)
Live weight gain (g/d) 606 480
o 0.001
29
20 552
448
0.008
34
381
351
0.141
20
496
445
0.09
29
80
41
0.002
11
51 76 104 197
Fig. 3. Mean calculated daily energy intakes of pasture (solid lines) and total feed (dotted lines) for red deer (solid triangles), F1 (solid circles) or F2 (open circles) calves. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
and 386 kg, respectively) producing more milk than hinds rearing red deer calves (325 kg; SED ¼24.2, P ¼0.024). There was no significant relationship between hind live weight and total lactation output, even when genotype was added as a grouping factor (Fig. 5). When average calf live weight was compared with hind milk output (Fig. 6) then a significant interaction between genotypes was apparent. There was a positive linear relationship between average calf live weight and hind milk production for both red hinds rearing red calves (P ¼0.072) and F1 hinds rearing F2 calves (P¼0.008). Approximately 14.6 kg more milk was produced for each extra kg of average calf liveweight at weaning. However, calf live weight had no significant effect on hind lactation output when red deer hinds were rearing F1 calves (P¼0.439). 4. Discussion
Fig. 2. Mean daily milk production of red deer rearing a red calf (solid triangle, dashed line) or an F1 calf (solid circle, solid line), or an F1 hind rearing an F2 calf (open circles, dotted line) during lactation. Standard error bars (sed) are represented as vertical lines at each measurement date. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the red deer calves when measured at birth (Fig. 4a), day 104 (Fig. 4b) and day 197 (Fig. 4c). 3.4. Total hind lactation output Calf genotype had a significant influence on total lactation output with hinds rearing F1 and F2 calves (393
The results need to be considered in two ways. The first is to compare the milk output of red hinds rearing red calves to that of F1 hinds rearing F2 calves: i.e. when hinds of disparate live weight rear calves of similar genotype to themselves. The second is to compare those outputs with that achieved by red hinds rearing an F1 calf. F1 hinds rearing F2 calves weighed more and produced more milk than red hinds rearing red calves. Carrion et al. (2008) reported daily milk production of Iberian red deer (C.e. hispanicus) hinds to be 18.7 mL/kg LW when accounting for other influences such as day of lactation. In the present study F1 hinds were, on average, 58.7 kg heavier than red hinds, and therefore had the potential to produce an extra 1.1 L milk/d above that of red hinds based on the data of Carrion et al. (2008). Landete-Castillejos et al. (2009) reported a total lactation yield of 2 L milk for each kg of hind live weight. Using that value, F1 hinds from the present study would be expected to produce an extra 117 L of milk during the course of the 126 d lactation reported, or approximately 0.6 L more milk/d, than that produced by red hinds rearing red calves. Indeed, the F1 hinds produced an average of 0.59 L more milk/d than red hinds to day 104
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Fig. 5. Hind live weight compared with milk production for red deer rearing a red calf (solid triangle) or an F1 calf (solid circle), or an F1 hind rearing an F2 calf (open circles) during lactation. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. Impacts of different calf genotypes on variability of calf liveweight (a) at birth and (b) at 104 days and (c) at 197 days of lactation. The box spans the interquartile range of the values in each variate, so that the middle 50% of the data lie within the box, with the line within the box indicating the median. Whiskers extend beyond the ends of the box as far as the minimum and maximum values.
and an extra 0.49 L milk/d on average over the experimental period of 197 days, though our hypothesis that greater calf demand determines milk production would also support this increase. Peak lactation yield, as calculated from NRC (2006) using the relationship by Oftendal (1984) where (NEL¼ 435 kJ BW0.70), suggests that the red deer hinds in this study had a theoretical peak lactation output of approximately 12 MJ/d, while the F1 hinds had a potential peak lactation output of approximately 16 MJ/d. These translate into milk yields of 2 and 2.6 kg/d. However, in this study, the milk output of red hinds rearing a red calf was
Fig. 6. Average calf live weight compared with the full season milk output of red deer hinds rearing red calves (solid triangle, dashed regression line; y¼11.55x 170, r2 ¼0.823) or F1 calves (solid circle, solid regression line; y¼ 550–3.26x, r2 ¼ 0.079), or F1 hinds rearing F2 calves (open circles, dotted regression line; y¼ 11.18x 145, r2 ¼ 0.615) during lactation.
approximately 2.9 kg/d, a red hind rearing an F1 calf was 3.7 kg/d and an F1 hind rearing an F2 calf was 3.9 kg/d. This suggests lactation outputs of 660 kJ/kg BW0.70 for red hinds rearing a red calf and F1 hinds rearing an F2 calf, but 800 kJ/kg BW0.70 for red hinds rearing an F1 calf. Results from Archer et al. (2013) indicated similar values of 653 and 854 kJ/kg BW0.70 produced by red hinds rearing red and F1 calves, respectively. It could be that calf demand, rather than hind live weight, is the main driver of hind milk production. This hypothesis is supported by red hinds rearing an F1 calf in this study having the same milk production as much larger F1 hinds rearing an F2 calf, demonstrating that calf demand has an important influence on milk production. However, the hind may be primed to provide the extra milk through in utero signals from the F1 calf. Evidence for this comes from the research of (Moore, 1966) who showed that ewe
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milk production is influenced by lamb genotype and suckling vigour and frequency. Cross fostering of Corriedale lambs to Merino ewes saw an increase in milk production over the same genotype suckling Merino lambs. Also, the increased suckling stimulus of twin lambs is the major reason for increased ewe milk production, which averages 41% more in twin bearing than single bearing ewes (Treacher, 1983). In the present study the udder score of red hinds rearing F1 calves was significantly greater than that of F1 hinds rearing F2 calves during peak lactation, indicating that a greater store of milk was being generated in response to higher demand. Although suckling observations in a previous study suggest that suckling frequency is unaffected by calf genotype, this may have been compensated for by larger calves sucking more vigorously (Ward et al., 2007). Udder score of the red hinds rearing an F1 calf indicated that a larger storage capacity may be available when required. However, the storage capacity of both red and F1 hinds rearing calves of like genotype appeared similar as represented by udder score, supporting the concept that much of the milk provided during a ‘normal’ lactation is produced on demand as suckling occurs. The evidence points to demand driving lactation when hind-calf genotype is the same, but pre-natal influences on mammogenesis cannot be ruled out when attempting to explain the response of the red hind rearing an F1 calf. However, pre-natal udder scores appeared to be related to potential birth date rather than indicating enhanced mammogenesis in red hinds carrying F1 calves as the pre-calving udder score of red and F1 hinds carrying crossbred calves with similarly late birth dates was similar and lower than red hinds carrying red calves with an earlier birth date. Differences in udder score were only noted post-parturition and reflected increased cistern capacity as the scoring system specifically relates to state of engorgement, although no definitive measurement of udder dimension was made. Data for F2 calves were more variable and provided a significant insight to what might be driving lactation as the hind live weights were much greater than those of the red dams. This is a really important point regarding the outcomes, as mean milk production increased by 14.6 kg/kg mean calf live weight over the 197 day lactation (R2 ¼0.50). Variability in F2 progeny is a common feature in crossbreeding programmes (Sorensen et al., 2008). Heterosis is greatest in the F1 and declines in the F2. Several studies in cattle suggest that the impacts of heterosis on milk yield are relatively low at between 2 and 8%, (Sorensen et al., 2008). Further, the impact of maternal heterosis on weaning weight is low in both cattle (Demeke et al., 2003; Kahi et al., 2000) and sheep (Geenty, 1979; Gootwine and Goot, 1996). Recombination effects are often negative (Sorensen et al., 2008) and may have influenced the performance of the F2 generation recorded in this experiment. The size of the relative effects of heterosis can be influenced by the type of cross breeding. In cattle of different species, Theunissen et al. (2013) reported that maternal heterosis was high in Bos taurus sanga progeny but not in Bos indicus sanga progeny, while the opposite was seen in individual heterosis. This may suggest that where relatively
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little selection pressure has been applied then a high degree of heterozygosity may already be present in the population, limiting the opportunity for heterosis. While the F1 and F2 calves did grow faster than the red calves, as predicted, the milk production of the hinds was relatively similar. The recombination of genes in the F2 calf appears to have resulted in high levels of phenotypic variation of F2 progeny with calf live weights ranging from the lowest to the highest average live weights recorded. However, the milk yield from red hinds rearing F1 calves was not related to calf live weight and indicated that milk production from the hind had reached a maximum at approximately 400 L milk over the 197 d lactation, and importantly, regardless of the size of the calf, following similar trends to other observations of milk yield from crossbred dams (Sorensen et al., 2008). This concept of approaching maximum milk output over the course of lactation when a red hind rears an F1 calf is supported by the lower BCS of those hinds compared to red hinds rearing red calves in early lactation. Red hinds rearing red calves and F1 hinds rearing F2 calves appeared to lose less BCS during early to peak lactation than those red hinds rearing an F1 calf. Use of body reserves to achieve the extra milk production may have been necessary to offset an inability to eat more feed to meet the extra energy requirement. This is a similar result to Archer et al. (2013) where extra energy requirement for lactation came from body reserves rather than feed intake, suggesting that under ‘normal’ conditions where the hind and the calf are of the same genotype then milk production is supported by feed intake unless feeding conditions are poor, as presented by Landete Castillejos et al. (2003). A decline in BCS was noted at approximately 120 days after calving in all hinds. While the red hinds recovered some of that loss, F1 hinds did not. However, milk production was relatively low at this point and the decline in production was similar for all hinds suggesting that this loss of condition at that time had little effect on total milk production. The F1 calf had a higher energy demand and greater growth rate than either the red or F2 calf. Both the red and F2 calves appeared to be behaving relatively similarly with respect to pasture intake. However, the F1 calves had a higher pasture energy intake to meet the greater demand. There was no evidence from Archer et al. (2013) that the F1 calf had greater feed conversion efficiency than the red calf, so the assumption that the F1 calf had a greater appetite for pasture due to a greater drive to grow is intuitive. Archer et al. (2013) found no significant difference between the pasture intakes of red or F1 calves, and assigned the difference in growth rate to the difference in milk intake. One potential reason for the difference between this experiment and that of Archer et al. (2013) is the higher milk intakes recorded in F1 calves in that study. These were approximately 0.4 L/d greater than those measured in this experiment, and may have been related to the larger hinds in that study. The use of F2 calves being suckled by F1 hinds provided a unique insight into the role of the calf in determining milk production in the hind, as this combination provided a significantly wide range of calf live weights that spanned
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those of the red and F1 calves to which they were compared, while providing hinds of much larger live weights. The evidence gathered using this approach, and the previous experiment by Archer et al. (2013), suggests that the generally held consensus that hind lactation output is driven by hind live weight may need modified. It appears that calf demand also plays a major part in driving lactation output from the hind. The hind then moderates the actual outcome depending on her ability to reach maximal milk output, which was achieved in this experiment with red wapiti calves suckling red deer hinds. Conflict of interest statement There are no conflicts of interest associated with the publication of this paper. Acknowledgements We are grateful to Lynne Rhodes for provision of AI services, and to Bruce Sinclair for analysis of deuterium content. This work was funded by the New Zealand Foundation of Research, Science and Technology (Contract C10 0709) and DEEResearch Ltd. References ARC, 1980. The Nutrient Requirements of Ruminant Livestock. Agricultural Research Council, Farnham Royal. Archer, J.A., Asher, G.W., Stevens, D.R., Ward, J.F., Scott, I.C., O’Neill, K.T., Littlejohn, R.P., Barrell, G.K., 2013. Influence of calf genotype on dam lactation and calf growth in farmed red deer (Cervus elaphus). Livest. Sci. 157, 289–298. Asher, G.W., Veldhuizen, F.A., Morrow, C.J., Duganzich, D.M., 1994. Effects of exogenous melatonin on prolactin secretion, lactogenesis and reproductive seasonality of adult female red deer (Cervus elaphus). J. Reprod. Fertil. 100, 11–19. Audige, L., Wilson, P.R., Morris, R.S., 1998. A body condition score system and its use for farmed red deer hinds. N.Z. J. Agric. Res. 41, 545–553. Blaxter, K.L., 1952. The nutrition of the young Ayrshire calf. 6. The utilisation of energy of whole milk. Br. J. Nutr. 16, 199–212. Carrion, D., Garcia, A.J., Gaspar-Lopez, E., Landete-Castillejos, T., Gallego, L., 2008. Development of body condition in hinds of Iberian red deer during gestation and its effects on calf birth weight and milk production. J. Exp. Zool. A: Ecol. Genet. Physiol. 309, 1–10. Demeke, S., Neser, F.W.C., Schoeman, S.J., 2003. Early growth performance of Bos taurus Bos indicus cattle crosses in Ethiopia: estimation of individual crossbreeding effects. J. Anim. Breed. Genet. 120, 245–257. Dove, H., 1988. Estimation of the intake of milk by lambs from the turnover of deuterium or tritium-labelled water. Br. J. Nutr. 60, 375–388. Dove, H., Freer, M., 1979. The accuracy of tritium labeled water turnover rate as an estimate of milk intake in lambs. Aust. J. Agric. Res. 30, 725–740.
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