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Influence of Protein Degradability and Evaporative Cooling on Performance of Dairy Cows During Hot Environmental Temperatures1
Influence of Protein Degradability and Evaporative Cooling on Performance of Dairy Cows During Hot Environmental Temperatures’ R. B. TAYLOR? J. T. HUBER? and A. A. GOMEZ-ALARCONQ Department of Animal Sciences F. WIERSMA and X. PANG Deparbmnt of Agriculhrral Engineering Universky of Arizona Tucson 86721
ing both trials, cooling demeased respiration rates and rectal temperatures, but protein degradability had no effect. The different production response between nidIs probably was due to hotter conditions and a higher quality of rumen undegradable protein in trial 2 than in rrial 1. Trial 2 data suggest that feeding of low degradable protein improves milk production duriug heat stress, provided the undegadable protein is of good quality(Key words: protein degradability, dairy cows, heat stress)
ABSTRACT
Two trials compared four treatments in a randomized block design with a 2 x 2 factorial arrangement of treatments using lactating Holstein cows. Factors were two concentrations of protein degradability (high, 61 to 64%; low, 47 to 55% degradable intake protein) and two types of environment (shading versus shading plus evaporative cooling). In trial 1 (24 cows for 55 d), evaporative cooling resulted in increases in production of milk, 3.5% FCM, gross efficiency of conversion of feed to milk, and DM intakes. The diet of greater protein degradability also increased milk production. There were no significant differences in milk composition. In trial 2 (36 cows for 50 d), cows fed less &gradable protein produced more milk of higher lactose and lower fat and protein contents. Protein degradability by evaporative cooling interactions were significant for milk production and efficiency of conversion of feed to milk, with the low degradable protein diet resulting in higher milk yields and efficiencies in cooled than in shaded cows. Dur-
Abbreviation key: HD = high degradable diet, LD = low degradable diet, THI = temperaturehumidity index. INTRODUCTION
Ambient temperature affects milk production during the hot summer months in southern Arizona (2). Heat stress increases the maintenance energy requirement and reduces milk yields and reproductive performance, causing serious economic losses (2, 12). Metabolism studies have shown that heat-stressed cattle undergo negative N balances (4, 11, 12). mainly due to reduced DM intakes. The reduced intakes result in less protein available for producReceived August 3, 1990. tive functions if concentrations of dietary proAccepted Febmuy 26,1990. l~rizona~ g ~ i ~ t u-t r a l station ~ ~ a m~arl t i - tein are not increased. A high protein diet cle Nnmba 7176. This papa is a contribution of Regional moderately high in rumen degradable protein Research Roject NC-171,Rediroding the Nutrient Flow in decreased performance of thermally stressed Cows for Maximum Milk Pmduction. *Present address: Rancho Ojo del Malpais. APDO cows more than a high protein diet of lower #115, Nucvo Casas Glades, Chihuahua, Mwico 31700. protein degradability (9).In other reports, pen %epriIll requests. evaporative cooling reduced heat stress, r e d t ‘hesent address: cmtr0 de Iwestigaciones, ~ecnarios del &tad0 dc Sonom APLW #1754, Hermosillo, Sonora, ing in increased milk yields and reproductive performance (2, 3). Mexico 83000. 1991 J Dairy Sci 74243-249
243
244
TAYLOR ET AL.
TABLE 1. merit and nuthxt composition of diets.' M
1
Trial2
Ingredients
m
LD
Alfalfa hay Whole Cottonseed Cottonseed hulls Ground corn Ground wheat soybean meal Corn gluten meal Blood meal
42.8 5
42.8 5
29.9 8.7 155
35.1 8.7
LD
HD (5% of DM)
MOlaSSeS
Animal fat Biofos' Calcium carbonate
Trace minerals, vitamios Nutrients
CP ADF NDF DIP, % of 8 mi, Mcaukg D I d
...
...
...
28.8 10.1 8.4 21.1 19.0
28.8 10.1 8.4 17.8 16.0 16.4
...
...
102
...
... ...
1.7 .3
1.7 .1 .4
...
...
2 2 2
.4 .2
2
17.8 26.7 31.7 60.8 1.65
18.1 29.8 39.2 46.8 1.62
... 2
...
...
5
5
18.8 235 28.1 63.7 1.73
18.4 22.6 29.7 54.9
1.72
5.8 4.1 1.8
1.8
IHD = High degradability; LD = low degmdabili& DIP = degradable intake protein, estimated from NRC (14). Estimates of DIP for ground corn, g r o d what, whole cottomeed, and cottonseed hulls were assumed to be the s m e as those in NRC (14) for corn, wheat, cottonseed meal, and cottonseed meal, respectively. Molasses contributed so little to diet protein that it was not included in degdability calculations. *A mixhue of monocalcium and dicalcium phosphates containing 21% P and 17% Ca. %or trials 1 and 2, respectively, the following were furnished (m& diet): Mn, 26.16; Zn, 32.22; Fe, 37,44, Cu,7, 5; Co, 1.6, .9;I, .4, .2; Se, .017, .Oll; vitaminA Qu/kg), 7600, 8200; vitamin & ( l a g ) llOO.lla0; vitamin E ( m a g ) 8,9. 'himated from NRC (14).
Because little is known about the effect of degradability and shade versus shade plus protein degradability during heat stress on milk evaporative cooling environmental modificaproduction and its interaction with evaporative tion. cooling, the objective of this study was to Cooling was accomplished by releasing undetermine the influence of dietary protein der pressure a fine mist from the water line degradability and evaporative cooling on dairy which was injected into an air stream blown by cow performance during hot summer months in fans mounted to a shade roof about 2.5 m from the ground ( K o d Cool Systems, Mesa, AZ). Tucson, Arizona Timers were set to activate the coolers only from O900 to 1600 h and from 2000 to O400 h MATERIALS AND HITHODS if ambient temperatures exceeded 29.4'C. A white polyethylene curtain situated on the west Trlal 1 side of the shade roof (generally the direction Twenty-four Holstein cows averaging 149 d of prevailing wind) was lowered automatically postpartum were used in a 55d lactation trial when coolers were activated. during August and September 1987. Cows were Diets (DM basis) were formulated (14) to placed in experimental pens during a 14-d pre- contain 20% CP, 1.65 McaVkg .65% Ca, treatment period. Blocks were formed on the and .a% P. However, the actual CP analysis basis of pretreatment milk production. Cows averaged 18.3% (Table 1). In both trials, solwere assigned randomly within blocks to four ventextracted soybean meal was the main protreatments arranged in a 2 by 2 factorial. Fac- tein supplement for the high degradable (HD) tors were: low versus high dietary protein diet, whereas the protein supplement for the
m,
Journal of Dairy Science Vol. 74, No. 1, 1991
245
PROTEIN DEGRADABILlTY AND EVAPORATWE COOI-lNG
TABLE 2. met of evaporative cooling on envimmnental temperatures atxi THI under pen W e s in trial 2.1 ~~
Mean daily maximam temperature, 'C Average temperatme? 'C Mean daily maximum THI Aveaage THI
COOled
Shadad
P<
31.3 26.9 80.0 15.7
36.9 29.3 82.7
.o 1
77.0
.01
.o 1 .o1
I T H I = Temperatare humidity index; calculated according to KmaI and Johmm (11). *Averaged hourly for the entire day during the 5 5 4 treatment period.
low degradable (LD) diet in trial 1 was corn gluten meal and corn gluten meal plus blood meal in trial 2. The blood meal was i n c o p rated to improve the quality of the undegmded protein, a factor suggested as beneficial in diets for high producing cows (16). Another difference between trials 1 and 2 was the addition of whole cottonseed in trial 2. Feed was sampled once weekly, and monthly composites were analyzed for CP by AOAC (1) procedures and ADF and NDF according to Robertson and Van Soest (15). Cows were weighed on 2 consecutive d at 7 d after the beginning and at the end of the triaL Experimental pens housed 12 cows each in an open lot (600 m2) and provided 48 m2 of concrete flooring at feeders. The two shaded areas in each pen were 72 mz; one was directly over the feeders; the other was in the center of the pens. Feeding was for ad libitum intake through electronic gates (American Calan Inc., Northwood, NH) to monitor individual feed intake. Feed refusal was recorded daily, and amount of feed offered was 10% in excess of appetite. Water (ca 20'C) and trace-mineralked salt blocks were available at all times. Cows were milked twice daily at 0700 and 1900 h, and milk yields were recorded every milking. Cows were fed once daily between 1100 and 1400 h. Representative samples of milk from a.m. and p.m. milkings from each cow were collected once weekly and composited. Milk samples were analyzed by the A r i z o ~DHI laboratory (Phoenix) for percentage fat, protein, lactose, and total solids by infrared analysis. Statistical analyses were conducted with BMDP (5) procedms using the following model:
This model accounts for overall mean, p; protein degradability, Di; evaporative cooling, Cj; protein degradability by evaporative cooling incovariate of prematment adteraction, %-* justed means for the variable under consideration COvk; and random error, &wIn trial 1, df associated with each variable were 1, 1, 1, 1, and 19, respectively. Trial 2 differed only in that there were 31 df for error. We chose Pc.05 to denote significant differences unless otherwise noted. Environmental temperature and humidity data were obtained from the Arizona meteorological Network (AZIvET), a service of the University of Arizona Cooperative Extension Service located approximately 1 Ian from the Dairy Research Center. Trial 2
Thirty-six Holstein cows averaging 135 d postpartum were used for a 50-d lactation trial during July and August 1988.Management was similar to that of trial 1. Diets were sampled weekly and composited monthly for analysis as described previously. Milking, feeding, weighing, statistical analyses, milk sampling, and other management practices were as described for trial 1. Eating patterns of 4 cows per treatment selected at random were evaluated during trial 2 by placing electronic interrupters on Calan gates. The interrupters were connected to a receiver that recorded the time when a gate was open or closed. When gates were open for less than 1 min, the interval was not considered a meal. When gates were closed for over 3 min, the meal was considered over. Wiring of gates did not inte~erewith the gate function nor animal behavior. The experimental period was 21 d. Statistical analyses were made by standard procedures (17)using the model described previously. Journal of Dairy Science Vol. 74, No. 1, 1991
246
TAYLOR ET AL.
TABLE 3. Effect of protein degradability and evaporaiive cooling on miIk yields and feed intakes.' ~~
Cooled Traits
HD
LD
HD
Shaded LD
Effects D
C
0 Trial 1 Milk prodnction FCM (3.5%) DM Intake M W D M intake Trial2 Milk production FCM (33%) DM Intake BW Change MilkIDM intalce
21.3 154
29.9 26.1 21.1 1.47
30.0 24.3 21.8 1.38
29.3 22.9 22.7 127
26.8 24.4 23.9 .80 1.18
32.8 26.4 21.6 .73 1.39
29.1 26.1 22.6 -.1 1.29
29.6 25.0 23.8 .36 1.24
31.9 25.7
DXC
P<
.w 57 .52 .14
.02 .75 .60 .30 .44
.o .a2
.31
.09
.37 .67
.01 .76 37 .64 .01
.94
.34
.04 .31 .09 20 -03
1Cov8ria~adjustedmeans. HD = High degdability; LD = low degradabiity; D = degdability &est C = coo&Et; D X C = intvxaction.
RESULTS AND DISCUSSION
Monitoring systems for coolers were not in place during trial 1, so only AZMET data assessed ambient conditions. h trial 2, the evaporative cooling system reduced maximum and average daily temperatures by 5.6 and 2.4'C, respectively, and maximum and average daily temperature-humidity indexes 0 by 2.7 and 2.3 (Table 2). Cooling apparently did not relieve all heat stress. Average THI under the evaporative coolers in trial 2 was 75.7. The critical THI above which milk yields are depressed in lactating dairy cows was reported to be 71 (2, 10). Daily THI indexes (reported by AZMET) for both trials are shown in Figure 1. During the first 2 wk, THI was similar for both trials, but there were large differences during the remaining weeks, with THI in trial 2 being higher than in trial 1. However, average THI for trial 1 exceeded 71 for all but about 16
that feed intakes should have favored the cooled cows (2, 13), but this was not the case, pernaps due to a higher maintenance requirement for uncooled cows (12). Cooled cows were more efficient in conversion of feed to milk because of higher milk yields and lower intakes (1.51 vs. 1.33 kg millr/kg DM). In trial 2, cooling by degradability interaction was significant for milk production and efficiency of conversion of feed to milk, with the LD cooled treatment higher than all others. There also was a tendency for a cooling by degradability interaction for feed intakes. When cooling was present, cows fed the HD diet showed higher feed intake, but without cooling,
Y
B
CI
d.
Milk yields, feed intakes, and changes in body weights are summarized in Table 3. In trial 1, both protein &gradability and pen cooling affected milk production. Evaporatively cooled cows produced 1.3 kg/d more milk than cows that received only shade. Cows on HD produced 1.4 kg/d more milk than those on LD. 1 4 7 W 18 to P 26 28 31 34 37 4 0 43 48 4 0 6 2 66 The FCM (3.5%) also was higher for evaporaDay of Trlal tively cooled (2.3 kg/d) than shaded cows. Feed 4 intakes for uncooled cows tended to be higher Figure 1. Mean daily temperature humidity index (10) than for cooled cows (P<.O9). It was expected for trials 1 and 2 (+ trial 1; 0 trial 2). ij
Journal of Dairy Science Vol. 74, No. 1, 1991
247
PROTEIN DEGRADABILITY AND EVAPORATIVE COOLING
TABLE 4. meet of protein degmlabiity and evaporative cooling on milk composition.' Cooled
HD
LD
HD
Shaded LD
Effects D
DxC
C
P<
(96) Trial1 Fat
Protein Lactose SIW Trial 2 Fat Protein
Lactose SIW
228 3.00 4.84 8.76
258 3.18 5.01 8.77
2.46 3.17 4.92 8.90
2.26 3.03 4.83
2.84 3.15 4.74 8.44
2.35 2.95 4.83 8.41
2.93 3.11 4.75 8.41
2.44 3.03 4.87 8.48
the LD cows ate more. The significant effect of cooling on mi& yields in trial 1, but not in trial 2, is difficult to explain, considering that THI were lower during trial 1 than during trial 2. However, in trial 2, the LD cows under coolers had higher production than all other groups. Final body weight data for trial 1 were lost, so only data from trial 2 are given. Cooling significantly increased weight gains, but degradability had no effect. A more positive energy balance resulting from cooling might have been partly responsible for improved reproductive performance of cooled cows in longer studies (2, 3). Efficiency of NE utilization was calculated for trial 2 [NE1 output (milk + tissue) + NE1 intake] according to NRC (14). The cooled LD treatment was highest (.a); other treatments were similar (ranging between .48 and S3). There were no significant treatment differences observed for any of the milk components in trial 1 (Table 4). In trial 2, the LD diet resulted in lower milk fat (2.40 vs. 2.89%, R.01) and milk protein (2.99 vs. 3.13%, Pe.01) but higher milk lactose (4.85 vs. 4.75%, R.01). The lower milk fat content on LD agrees with other studies that reported decreased milk fat in cows fed protein soufces of low degradability (6,7,8). Percentages of fat in milk were below what might normally be expected. However, other studies have shown similarly low values for milk fat percentage when cows were fed high concentrate diets during heat stress (9, 12).
8.77
.80 .39 .69 .76
.74 .62 .62 .72
.01
.s7 .73
.01 .01 .95
24 .18
24 .69
SO
.98 23 .76
.43
50
The relative advantage of LD over HD diets in milk yields of cooled cows during trial 2, coupled with higher milk on HD in trial 1, could have been due to higher quality protein exiting the rumen of LD cows in trial 2. Blood meal and com gluten meal complement each other, because blood meal is low in isoleucine @e) and methionine (Met), but high in -tophan (Trp) and lysine (Lys), whereas corn gluten meal is low in Trp and Lys (16) but higher than blood meal in ne and Met. Higginbotham et aI. (7, 9) conducted three trials in Arizona (summer) and one in Utah (spring) to compare diets of differing protein percentages and rumen degradabilities. The Arizona trials were conducted at the same facilities used for our trial, but evaporative cooling equipment had not yet been installed. In the Arizona trials (9), high protein diets of high rumen degradability decreased milk production, whereas the same diet resulted in highest milk production in the Utah trial (7). A similar trend was seen in the present study under the hotter environmental conditions of trial 2 as compared with the more moderate conditions of trial 1. Cows fed the LD diet produced more milk than those fed HD in trial 2 at hotter ambient temperatures, but were lower than the HD in trial 1 under cooler conditions. However, this trend was not seen when comparing cooled to shaded cows within each trial. Cooling decreased respiration rates in trial 1 (Table 5 ) as cooled cows exhibited 12 respirationshnh less than shaded cows. Protein Journal of Dairy Science Vol. 74, No. 1. 1991
248
TAYLOR ET AL.
TABLE 5. Effect of protein dtsradability and evaporative cooling on respiration rntes, rectal temperatu~,total tating time and meals per day of cows in both trials.1 ~~
HD
Trial
LD
~-
~~~
Shaded
Cooled
HD
LD
Effects D
DXC
C
P< Trial1 Respirationspermimrte Rectal temperature, 'C T i m eating, min Meals p a day Trial 2 Respiratioospermirmte Rcaal temperature, 'C T i m eating, min Meals p a day
77 39.0 166 9.0
74 38.8 222 11.0
86 38.9 247 9.6
89 39.3 149 9.4
75 39.4 216 10.6
66 39.1 186 9.4
81 39.7 192 8.7
95 39.7 194 9.5
.61
.01 .17 .45 59
.37 .05 .02 .37
.42 24 .39 .75
.01 .01 .69 .15
.01
.85 .74
.90
.40 27 .12
lCovaria~adjrrstedmeans. HD = High degradability; LD = low degradabilifl; D = degradability &et;C = cooling
effect; D x C = interaction.
degradability by cooling interaction was significant for rectal temperatures. 'when cooling was present, cows fed the LD diet had lower temperatures than those fed HD,but without cooling, cows fed the LD diet had higher rectal temperatures than those fed HD. Neither protein percentage nor degradability consistently affected mtaI temperatures in the previous trials (7, 9); however, in one trial at hot temperatures (9), cows fed high protein diets exhibited lower rectal temperatures at high than low degradability, perhaps due to the intake of about 20% more water by HD cows in the study by Higginbotham et aL (9). In trial 2, a significant protein degradability by cooling interaction was observed for respiration rates. When cooling was present, cows fed the LD diet had lower respiration rates, but in the shade, LD cows were higher. An overall cooling effect also was detected with cooled cows having 17.5 respirations/min less than uncooled cows. Rectal temperames also exhibited a cooling effect, with cooled cows being .45'C lower than the uncooled ones. Neither degradability nor cooling significantly affected time spent eating (197 W d ) , but there was an interaction during trial 1; LD cows ate longer than HD cows when cooled but less when only shade was provided The reason far this interaction is not clear. Also, number of meals (9.6/d) was not affected by treatments. Results of this study indicate that evaporative coolers changed environmental conditions Journal of Dairy Scicnce Vol. 74, No. 1. 1991
enough to improve milk production in three of four direct comparisons with cows receiving only shade. However, changes due to evaporative cooling were not sufficient to duplicate effects of a naturally cool environment (7). These data further suggest that protein degradability and evaporative cooling differentially affect dairy cow performance, depending on seventy of thermal stress and quality of dietary protein. However, when thennal stress was greatest (in trial 2), cooled cows on the LD diet produced more milk than uncooled LD cows or than either cooled or uncooled cows on the HD diet. Greater heat stress may have masked a beneficial response to LD compared with response to HD in uncooled cows in trial 2. REFERENCES 1Association of official Analchemists. 1980. official methods of analysis. 12th ed. Assoc. Of& Anal. chcm,Washington. Dc. 2Armsmng, D. V., and F. Wiersma. 1986. An update on cow cooling methods in tbe West.No. 86-4034, Am. Soc. Agric. Eng. Microfiche C~liectio4 St, Joseph, MI. 3Armstrong.D. V., F.Wiersma, T. J. EEllhrmann. J. M. Tappan, and S. M.Cnuncr. 1985. Effect of evaporative cooling aodcr a corral slnule on reproduction and milk prodaction in a hot-arid climate. J. Dairy Sci. 68(Soppl. 1):167. (Abetr.) 4Baedc. D.K., and R. J. Collin. 1986. PotentiaI mihitionnl strategies for intensively managed cattle during thamal stress. I. Anim. Sci. 62543. SBio-M~dicalData Rognuns. 1985. Analysis O f variance and covariance with repeated meanues. BMDP statisticat software, Inc., univ. California$ Los
PROTEIN DEGRADABILITY AND EVAPORATIVE COOLING Angelcs. 6Block, E., L. L. Muller, L. L. e e l , Jr., and D. L. Garwood. 1981. Brown m i h i 3 corn silage ami heatextruded soybeans for early lactating dairy cows. J. Dairy Sci. M1813. 7Higginbotbam, G.E., J. T. Hubex, W. V. Wallentine, N. P. Johnston, and D. Andrus. 1989. Influence of protein percmt and &gradability on performance of lactating cows during moderate temperature. J. Dairy Sci. 72:1818. 8H@iubotbm, G. E., N. P. Johnston. D. D. Aadms. and J. T. H u k . 1984. Effect of m*potein nitrogen w'on of highly insoluble dairy rations on theperformaIlceofhighprodacingdairycows.J.Dairy Sci. 67(Suppl. 1):120. (AM.) 9Higginbotham, G. E., h4. Tombi, and J. T. H u b . 1989. Influence of dietary protein consenbution d d e ~ t y o n p e r f o r m a n c eoflamtiogcowamahrg hot env' . 1 tempemtures. J. Dairy Sci. 7225%. 10 Johnson.H.D., and W. J. Vanjonack. 1976. Effects of environmental and other sfressors on blood hormone paio lactating cows. 1. Dairy Sci. 591603. 11 Kamal, T. H.. and H. D. Johnson. 1970. Whole body
249
4OK loss M a predictor of heat tolemnce in catik. 1. Dairy Sci. 58:1734. 12 MdDowcll, R E., E. G. Moody,P. 3. Van Socst, R. P. Lebmau, and G.L. Ford. 1969. Effect of beat stress on mrgy and watu utilization of lactating cows. 3. Dairy Sci. 52188. 13 Mohammad, M.E., and H. D. Joimson. 1985. Effect of growth hormone on milk yields and related physiological fnnctioos of Holstein cows exposed to heat stress. J. Dairy Sci. 68:1123. 14National Research Council. 1989. Nutrient requirements of dairy cattle. 6th xw. ed. Natl. A d Press, Washingtoq Dc. 1SRobertson. J. B.. and P. J. VM Sast 1981. The detpgmt system of analysis and its application to human foods. Page 123 in 'Lhe enalysis of dietary fiber in food Vol. 3, W.P.T. James and 0. Tbmder, ed. Marcel DewEcr, h., New York, NY. C. G. 1989. Amino acids io dairy COW mtri16 SC-, tion. €%ge 75 in Rbsnapouknc Animal Nutrition Tccbnid Symposium, Fresno. CA. 1 7 S e l , R.G.D., and J. H. T h e . 1980. Principles and PrOcedareJof atistics. McGraw-Hin, N ~ wYO&, NY.
Journal of Dahy Science Vol. 74, No. 1, 1991
ing both trials, cooling demeased respiration rates and rectal temperatures, but protein degradability had no effect. The different production response between nidIs probably was due to hotter conditions and a higher quality of rumen undegradable protein in trial 2 than in rrial 1. Trial 2 data suggest that feeding of low degradable protein improves milk production duriug heat stress, provided the undegadable protein is of good quality(Key words: protein degradability, dairy cows, heat stress)
ABSTRACT
Two trials compared four treatments in a randomized block design with a 2 x 2 factorial arrangement of treatments using lactating Holstein cows. Factors were two concentrations of protein degradability (high, 61 to 64%; low, 47 to 55% degradable intake protein) and two types of environment (shading versus shading plus evaporative cooling). In trial 1 (24 cows for 55 d), evaporative cooling resulted in increases in production of milk, 3.5% FCM, gross efficiency of conversion of feed to milk, and DM intakes. The diet of greater protein degradability also increased milk production. There were no significant differences in milk composition. In trial 2 (36 cows for 50 d), cows fed less &gradable protein produced more milk of higher lactose and lower fat and protein contents. Protein degradability by evaporative cooling interactions were significant for milk production and efficiency of conversion of feed to milk, with the low degradable protein diet resulting in higher milk yields and efficiencies in cooled than in shaded cows. Dur-
Abbreviation key: HD = high degradable diet, LD = low degradable diet, THI = temperaturehumidity index. INTRODUCTION
Ambient temperature affects milk production during the hot summer months in southern Arizona (2). Heat stress increases the maintenance energy requirement and reduces milk yields and reproductive performance, causing serious economic losses (2, 12). Metabolism studies have shown that heat-stressed cattle undergo negative N balances (4, 11, 12). mainly due to reduced DM intakes. The reduced intakes result in less protein available for producReceived August 3, 1990. tive functions if concentrations of dietary proAccepted Febmuy 26,1990. l~rizona~ g ~ i ~ t u-t r a l station ~ ~ a m~arl t i - tein are not increased. A high protein diet cle Nnmba 7176. This papa is a contribution of Regional moderately high in rumen degradable protein Research Roject NC-171,Rediroding the Nutrient Flow in decreased performance of thermally stressed Cows for Maximum Milk Pmduction. *Present address: Rancho Ojo del Malpais. APDO cows more than a high protein diet of lower #115, Nucvo Casas Glades, Chihuahua, Mwico 31700. protein degradability (9).In other reports, pen %epriIll requests. evaporative cooling reduced heat stress, r e d t ‘hesent address: cmtr0 de Iwestigaciones, ~ecnarios del &tad0 dc Sonom APLW #1754, Hermosillo, Sonora, ing in increased milk yields and reproductive performance (2, 3). Mexico 83000. 1991 J Dairy Sci 74243-249
243
244
TAYLOR ET AL.
TABLE 1. merit and nuthxt composition of diets.' M
1
Trial2
Ingredients
m
LD
Alfalfa hay Whole Cottonseed Cottonseed hulls Ground corn Ground wheat soybean meal Corn gluten meal Blood meal
42.8 5
42.8 5
29.9 8.7 155
35.1 8.7
LD
HD (5% of DM)
MOlaSSeS
Animal fat Biofos' Calcium carbonate
Trace minerals, vitamios Nutrients
CP ADF NDF DIP, % of 8 mi, Mcaukg D I d
...
...
...
28.8 10.1 8.4 21.1 19.0
28.8 10.1 8.4 17.8 16.0 16.4
...
...
102
...
... ...
1.7 .3
1.7 .1 .4
...
...
2 2 2
.4 .2
2
17.8 26.7 31.7 60.8 1.65
18.1 29.8 39.2 46.8 1.62
... 2
...
...
5
5
18.8 235 28.1 63.7 1.73
18.4 22.6 29.7 54.9
1.72
5.8 4.1 1.8
1.8
IHD = High degradability; LD = low degmdabili& DIP = degradable intake protein, estimated from NRC (14). Estimates of DIP for ground corn, g r o d what, whole cottomeed, and cottonseed hulls were assumed to be the s m e as those in NRC (14) for corn, wheat, cottonseed meal, and cottonseed meal, respectively. Molasses contributed so little to diet protein that it was not included in degdability calculations. *A mixhue of monocalcium and dicalcium phosphates containing 21% P and 17% Ca. %or trials 1 and 2, respectively, the following were furnished (m& diet): Mn, 26.16; Zn, 32.22; Fe, 37,44, Cu,7, 5; Co, 1.6, .9;I, .4, .2; Se, .017, .Oll; vitaminA Qu/kg), 7600, 8200; vitamin & ( l a g ) llOO.lla0; vitamin E ( m a g ) 8,9. 'himated from NRC (14).
Because little is known about the effect of degradability and shade versus shade plus protein degradability during heat stress on milk evaporative cooling environmental modificaproduction and its interaction with evaporative tion. cooling, the objective of this study was to Cooling was accomplished by releasing undetermine the influence of dietary protein der pressure a fine mist from the water line degradability and evaporative cooling on dairy which was injected into an air stream blown by cow performance during hot summer months in fans mounted to a shade roof about 2.5 m from the ground ( K o d Cool Systems, Mesa, AZ). Tucson, Arizona Timers were set to activate the coolers only from O900 to 1600 h and from 2000 to O400 h MATERIALS AND HITHODS if ambient temperatures exceeded 29.4'C. A white polyethylene curtain situated on the west Trlal 1 side of the shade roof (generally the direction Twenty-four Holstein cows averaging 149 d of prevailing wind) was lowered automatically postpartum were used in a 55d lactation trial when coolers were activated. during August and September 1987. Cows were Diets (DM basis) were formulated (14) to placed in experimental pens during a 14-d pre- contain 20% CP, 1.65 McaVkg .65% Ca, treatment period. Blocks were formed on the and .a% P. However, the actual CP analysis basis of pretreatment milk production. Cows averaged 18.3% (Table 1). In both trials, solwere assigned randomly within blocks to four ventextracted soybean meal was the main protreatments arranged in a 2 by 2 factorial. Fac- tein supplement for the high degradable (HD) tors were: low versus high dietary protein diet, whereas the protein supplement for the
m,
Journal of Dairy Science Vol. 74, No. 1, 1991
245
PROTEIN DEGRADABILlTY AND EVAPORATWE COOI-lNG
TABLE 2. met of evaporative cooling on envimmnental temperatures atxi THI under pen W e s in trial 2.1 ~~
Mean daily maximam temperature, 'C Average temperatme? 'C Mean daily maximum THI Aveaage THI
COOled
Shadad
P<
31.3 26.9 80.0 15.7
36.9 29.3 82.7
.o 1
77.0
.01
.o 1 .o1
I T H I = Temperatare humidity index; calculated according to KmaI and Johmm (11). *Averaged hourly for the entire day during the 5 5 4 treatment period.
low degradable (LD) diet in trial 1 was corn gluten meal and corn gluten meal plus blood meal in trial 2. The blood meal was i n c o p rated to improve the quality of the undegmded protein, a factor suggested as beneficial in diets for high producing cows (16). Another difference between trials 1 and 2 was the addition of whole cottonseed in trial 2. Feed was sampled once weekly, and monthly composites were analyzed for CP by AOAC (1) procedures and ADF and NDF according to Robertson and Van Soest (15). Cows were weighed on 2 consecutive d at 7 d after the beginning and at the end of the triaL Experimental pens housed 12 cows each in an open lot (600 m2) and provided 48 m2 of concrete flooring at feeders. The two shaded areas in each pen were 72 mz; one was directly over the feeders; the other was in the center of the pens. Feeding was for ad libitum intake through electronic gates (American Calan Inc., Northwood, NH) to monitor individual feed intake. Feed refusal was recorded daily, and amount of feed offered was 10% in excess of appetite. Water (ca 20'C) and trace-mineralked salt blocks were available at all times. Cows were milked twice daily at 0700 and 1900 h, and milk yields were recorded every milking. Cows were fed once daily between 1100 and 1400 h. Representative samples of milk from a.m. and p.m. milkings from each cow were collected once weekly and composited. Milk samples were analyzed by the A r i z o ~DHI laboratory (Phoenix) for percentage fat, protein, lactose, and total solids by infrared analysis. Statistical analyses were conducted with BMDP (5) procedms using the following model:
This model accounts for overall mean, p; protein degradability, Di; evaporative cooling, Cj; protein degradability by evaporative cooling incovariate of prematment adteraction, %-* justed means for the variable under consideration COvk; and random error, &wIn trial 1, df associated with each variable were 1, 1, 1, 1, and 19, respectively. Trial 2 differed only in that there were 31 df for error. We chose Pc.05 to denote significant differences unless otherwise noted. Environmental temperature and humidity data were obtained from the Arizona meteorological Network (AZIvET), a service of the University of Arizona Cooperative Extension Service located approximately 1 Ian from the Dairy Research Center. Trial 2
Thirty-six Holstein cows averaging 135 d postpartum were used for a 50-d lactation trial during July and August 1988.Management was similar to that of trial 1. Diets were sampled weekly and composited monthly for analysis as described previously. Milking, feeding, weighing, statistical analyses, milk sampling, and other management practices were as described for trial 1. Eating patterns of 4 cows per treatment selected at random were evaluated during trial 2 by placing electronic interrupters on Calan gates. The interrupters were connected to a receiver that recorded the time when a gate was open or closed. When gates were open for less than 1 min, the interval was not considered a meal. When gates were closed for over 3 min, the meal was considered over. Wiring of gates did not inte~erewith the gate function nor animal behavior. The experimental period was 21 d. Statistical analyses were made by standard procedures (17)using the model described previously. Journal of Dairy Science Vol. 74, No. 1, 1991
246
TAYLOR ET AL.
TABLE 3. Effect of protein degradability and evaporaiive cooling on miIk yields and feed intakes.' ~~
Cooled Traits
HD
LD
HD
Shaded LD
Effects D
C
0 Trial 1 Milk prodnction FCM (3.5%) DM Intake M W D M intake Trial2 Milk production FCM (33%) DM Intake BW Change MilkIDM intalce
21.3 154
29.9 26.1 21.1 1.47
30.0 24.3 21.8 1.38
29.3 22.9 22.7 127
26.8 24.4 23.9 .80 1.18
32.8 26.4 21.6 .73 1.39
29.1 26.1 22.6 -.1 1.29
29.6 25.0 23.8 .36 1.24
31.9 25.7
DXC
P<
.w 57 .52 .14
.02 .75 .60 .30 .44
.o .a2
.31
.09
.37 .67
.01 .76 37 .64 .01
.94
.34
.04 .31 .09 20 -03
1Cov8ria~adjustedmeans. HD = High degdability; LD = low degradabiity; D = degdability &est C = coo&Et; D X C = intvxaction.
RESULTS AND DISCUSSION
Monitoring systems for coolers were not in place during trial 1, so only AZMET data assessed ambient conditions. h trial 2, the evaporative cooling system reduced maximum and average daily temperatures by 5.6 and 2.4'C, respectively, and maximum and average daily temperature-humidity indexes 0 by 2.7 and 2.3 (Table 2). Cooling apparently did not relieve all heat stress. Average THI under the evaporative coolers in trial 2 was 75.7. The critical THI above which milk yields are depressed in lactating dairy cows was reported to be 71 (2, 10). Daily THI indexes (reported by AZMET) for both trials are shown in Figure 1. During the first 2 wk, THI was similar for both trials, but there were large differences during the remaining weeks, with THI in trial 2 being higher than in trial 1. However, average THI for trial 1 exceeded 71 for all but about 16
that feed intakes should have favored the cooled cows (2, 13), but this was not the case, pernaps due to a higher maintenance requirement for uncooled cows (12). Cooled cows were more efficient in conversion of feed to milk because of higher milk yields and lower intakes (1.51 vs. 1.33 kg millr/kg DM). In trial 2, cooling by degradability interaction was significant for milk production and efficiency of conversion of feed to milk, with the LD cooled treatment higher than all others. There also was a tendency for a cooling by degradability interaction for feed intakes. When cooling was present, cows fed the HD diet showed higher feed intake, but without cooling,
Y
B
CI
d.
Milk yields, feed intakes, and changes in body weights are summarized in Table 3. In trial 1, both protein &gradability and pen cooling affected milk production. Evaporatively cooled cows produced 1.3 kg/d more milk than cows that received only shade. Cows on HD produced 1.4 kg/d more milk than those on LD. 1 4 7 W 18 to P 26 28 31 34 37 4 0 43 48 4 0 6 2 66 The FCM (3.5%) also was higher for evaporaDay of Trlal tively cooled (2.3 kg/d) than shaded cows. Feed 4 intakes for uncooled cows tended to be higher Figure 1. Mean daily temperature humidity index (10) than for cooled cows (P<.O9). It was expected for trials 1 and 2 (+ trial 1; 0 trial 2). ij
Journal of Dairy Science Vol. 74, No. 1, 1991
247
PROTEIN DEGRADABILITY AND EVAPORATIVE COOLING
TABLE 4. meet of protein degmlabiity and evaporative cooling on milk composition.' Cooled
HD
LD
HD
Shaded LD
Effects D
DxC
C
P<
(96) Trial1 Fat
Protein Lactose SIW Trial 2 Fat Protein
Lactose SIW
228 3.00 4.84 8.76
258 3.18 5.01 8.77
2.46 3.17 4.92 8.90
2.26 3.03 4.83
2.84 3.15 4.74 8.44
2.35 2.95 4.83 8.41
2.93 3.11 4.75 8.41
2.44 3.03 4.87 8.48
the LD cows ate more. The significant effect of cooling on mi& yields in trial 1, but not in trial 2, is difficult to explain, considering that THI were lower during trial 1 than during trial 2. However, in trial 2, the LD cows under coolers had higher production than all other groups. Final body weight data for trial 1 were lost, so only data from trial 2 are given. Cooling significantly increased weight gains, but degradability had no effect. A more positive energy balance resulting from cooling might have been partly responsible for improved reproductive performance of cooled cows in longer studies (2, 3). Efficiency of NE utilization was calculated for trial 2 [NE1 output (milk + tissue) + NE1 intake] according to NRC (14). The cooled LD treatment was highest (.a); other treatments were similar (ranging between .48 and S3). There were no significant treatment differences observed for any of the milk components in trial 1 (Table 4). In trial 2, the LD diet resulted in lower milk fat (2.40 vs. 2.89%, R.01) and milk protein (2.99 vs. 3.13%, Pe.01) but higher milk lactose (4.85 vs. 4.75%, R.01). The lower milk fat content on LD agrees with other studies that reported decreased milk fat in cows fed protein soufces of low degradability (6,7,8). Percentages of fat in milk were below what might normally be expected. However, other studies have shown similarly low values for milk fat percentage when cows were fed high concentrate diets during heat stress (9, 12).
8.77
.80 .39 .69 .76
.74 .62 .62 .72
.01
.s7 .73
.01 .01 .95
24 .18
24 .69
SO
.98 23 .76
.43
50
The relative advantage of LD over HD diets in milk yields of cooled cows during trial 2, coupled with higher milk on HD in trial 1, could have been due to higher quality protein exiting the rumen of LD cows in trial 2. Blood meal and com gluten meal complement each other, because blood meal is low in isoleucine @e) and methionine (Met), but high in -tophan (Trp) and lysine (Lys), whereas corn gluten meal is low in Trp and Lys (16) but higher than blood meal in ne and Met. Higginbotham et aI. (7, 9) conducted three trials in Arizona (summer) and one in Utah (spring) to compare diets of differing protein percentages and rumen degradabilities. The Arizona trials were conducted at the same facilities used for our trial, but evaporative cooling equipment had not yet been installed. In the Arizona trials (9), high protein diets of high rumen degradability decreased milk production, whereas the same diet resulted in highest milk production in the Utah trial (7). A similar trend was seen in the present study under the hotter environmental conditions of trial 2 as compared with the more moderate conditions of trial 1. Cows fed the LD diet produced more milk than those fed HD in trial 2 at hotter ambient temperatures, but were lower than the HD in trial 1 under cooler conditions. However, this trend was not seen when comparing cooled to shaded cows within each trial. Cooling decreased respiration rates in trial 1 (Table 5 ) as cooled cows exhibited 12 respirationshnh less than shaded cows. Protein Journal of Dairy Science Vol. 74, No. 1. 1991
248
TAYLOR ET AL.
TABLE 5. Effect of protein dtsradability and evaporative cooling on respiration rntes, rectal temperatu~,total tating time and meals per day of cows in both trials.1 ~~
HD
Trial
LD
~-
~~~
Shaded
Cooled
HD
LD
Effects D
DXC
C
P< Trial1 Respirationspermimrte Rectal temperature, 'C T i m eating, min Meals p a day Trial 2 Respiratioospermirmte Rcaal temperature, 'C T i m eating, min Meals p a day
77 39.0 166 9.0
74 38.8 222 11.0
86 38.9 247 9.6
89 39.3 149 9.4
75 39.4 216 10.6
66 39.1 186 9.4
81 39.7 192 8.7
95 39.7 194 9.5
.61
.01 .17 .45 59
.37 .05 .02 .37
.42 24 .39 .75
.01 .01 .69 .15
.01
.85 .74
.90
.40 27 .12
lCovaria~adjrrstedmeans. HD = High degradability; LD = low degradabilifl; D = degradability &et;C = cooling
effect; D x C = interaction.
degradability by cooling interaction was significant for rectal temperatures. 'when cooling was present, cows fed the LD diet had lower temperatures than those fed HD,but without cooling, cows fed the LD diet had higher rectal temperatures than those fed HD. Neither protein percentage nor degradability consistently affected mtaI temperatures in the previous trials (7, 9); however, in one trial at hot temperatures (9), cows fed high protein diets exhibited lower rectal temperatures at high than low degradability, perhaps due to the intake of about 20% more water by HD cows in the study by Higginbotham et aL (9). In trial 2, a significant protein degradability by cooling interaction was observed for respiration rates. When cooling was present, cows fed the LD diet had lower respiration rates, but in the shade, LD cows were higher. An overall cooling effect also was detected with cooled cows having 17.5 respirations/min less than uncooled cows. Rectal temperames also exhibited a cooling effect, with cooled cows being .45'C lower than the uncooled ones. Neither degradability nor cooling significantly affected time spent eating (197 W d ) , but there was an interaction during trial 1; LD cows ate longer than HD cows when cooled but less when only shade was provided The reason far this interaction is not clear. Also, number of meals (9.6/d) was not affected by treatments. Results of this study indicate that evaporative coolers changed environmental conditions Journal of Dairy Scicnce Vol. 74, No. 1. 1991
enough to improve milk production in three of four direct comparisons with cows receiving only shade. However, changes due to evaporative cooling were not sufficient to duplicate effects of a naturally cool environment (7). These data further suggest that protein degradability and evaporative cooling differentially affect dairy cow performance, depending on seventy of thermal stress and quality of dietary protein. However, when thennal stress was greatest (in trial 2), cooled cows on the LD diet produced more milk than uncooled LD cows or than either cooled or uncooled cows on the HD diet. Greater heat stress may have masked a beneficial response to LD compared with response to HD in uncooled cows in trial 2. REFERENCES 1Association of official Analchemists. 1980. official methods of analysis. 12th ed. Assoc. Of& Anal. chcm,Washington. Dc. 2Armsmng, D. V., and F. Wiersma. 1986. An update on cow cooling methods in tbe West.No. 86-4034, Am. Soc. Agric. Eng. Microfiche C~liectio4 St, Joseph, MI. 3Armstrong.D. V., F.Wiersma, T. J. EEllhrmann. J. M. Tappan, and S. M.Cnuncr. 1985. Effect of evaporative cooling aodcr a corral slnule on reproduction and milk prodaction in a hot-arid climate. J. Dairy Sci. 68(Soppl. 1):167. (Abetr.) 4Baedc. D.K., and R. J. Collin. 1986. PotentiaI mihitionnl strategies for intensively managed cattle during thamal stress. I. Anim. Sci. 62543. SBio-M~dicalData Rognuns. 1985. Analysis O f variance and covariance with repeated meanues. BMDP statisticat software, Inc., univ. California$ Los
PROTEIN DEGRADABILITY AND EVAPORATIVE COOLING Angelcs. 6Block, E., L. L. Muller, L. L. e e l , Jr., and D. L. Garwood. 1981. Brown m i h i 3 corn silage ami heatextruded soybeans for early lactating dairy cows. J. Dairy Sci. M1813. 7Higginbotbam, G.E., J. T. Hubex, W. V. Wallentine, N. P. Johnston, and D. Andrus. 1989. Influence of protein percmt and &gradability on performance of lactating cows during moderate temperature. J. Dairy Sci. 72:1818. 8H@iubotbm, G. E., N. P. Johnston. D. D. Aadms. and J. T. H u k . 1984. Effect of m*potein nitrogen w'on of highly insoluble dairy rations on theperformaIlceofhighprodacingdairycows.J.Dairy Sci. 67(Suppl. 1):120. (AM.) 9Higginbotham, G. E., h4. Tombi, and J. T. H u b . 1989. Influence of dietary protein consenbution d d e ~ t y o n p e r f o r m a n c eoflamtiogcowamahrg hot env' . 1 tempemtures. J. Dairy Sci. 7225%. 10 Johnson.H.D., and W. J. Vanjonack. 1976. Effects of environmental and other sfressors on blood hormone paio lactating cows. 1. Dairy Sci. 591603. 11 Kamal, T. H.. and H. D. Johnson. 1970. Whole body
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4OK loss M a predictor of heat tolemnce in catik. 1. Dairy Sci. 58:1734. 12 MdDowcll, R E., E. G. Moody,P. 3. Van Socst, R. P. Lebmau, and G.L. Ford. 1969. Effect of beat stress on mrgy and watu utilization of lactating cows. 3. Dairy Sci. 52188. 13 Mohammad, M.E., and H. D. Joimson. 1985. Effect of growth hormone on milk yields and related physiological fnnctioos of Holstein cows exposed to heat stress. J. Dairy Sci. 68:1123. 14National Research Council. 1989. Nutrient requirements of dairy cattle. 6th xw. ed. Natl. A d Press, Washingtoq Dc. 1SRobertson. J. B.. and P. J. VM Sast 1981. The detpgmt system of analysis and its application to human foods. Page 123 in 'Lhe enalysis of dietary fiber in food Vol. 3, W.P.T. James and 0. Tbmder, ed. Marcel DewEcr, h., New York, NY. C. G. 1989. Amino acids io dairy COW mtri16 SC-, tion. €%ge 75 in Rbsnapouknc Animal Nutrition Tccbnid Symposium, Fresno. CA. 1 7 S e l , R.G.D., and J. H. T h e . 1980. Principles and PrOcedareJof atistics. McGraw-Hin, N ~ wYO&, NY.
Journal of Dahy Science Vol. 74, No. 1, 1991