Influence of Nutrient Supplementation on Body Weight and Condition and Pregnancy of Market Beef Cows Grazing Stockpiled and Spring-Growth Tall Fescue1

The Professional Animal Scientist 21 (2005):225–231

Influence of Nutrient Supplementation on Body Weight and Condition and Pregnancy of Market Beef Cows Grazing Stockpiled and Spring-Growth Tall 1 Fescue M. L. LOOPER*2, PAS, G. E. AIKEN†, PAS, R. FLORES‡, PAS, and C. F. ROSENKRANS, JR.‡ *USDA, ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927; †USDA, ARS, ForageAnimal Production Research Unit, Lexington, KY 40546; ‡Department of Animal Science, University of Arkansas, Fayetteville 72701

Abstract Seventy-five crossbred, non-pregnant beef cows [age = 4.5 ± 0.2 yr; BW = 395 ± 10 kg; body condition score (BCS) = 4.3 ± 0.2] were purchased from local auctions during 2 yr to determine the effects of supplementation on BW, BCS, ADG, pregnancy rate, and net income of market cows grazing stockpiled and spring-growth, endophyte-infected tall fescue (Festuca arundinacea Schreb.). Cows were assigned to one of six pastures (two pastures per treatment each year) of tall fescue for 160 d (yr 1) or 147 d (yr 2) and one of three supplemen-

1

Names are necessary to report factually on available data; however, the USDA does not guarantee or warrant the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that also may be suitable. 2 To whom correspondence should be addressed: [email protected]

tation treatments: 1) soybean hulls (SH), 2) corn:soybean meal (CSB), or 3) not supplemented (control). Supplements were fed at 0.91 kg/d per cow. Cows were sold at a local auction at the termination of the experiment. Forage availability was not affected (P>0.10) by supplementation and averaged 3637 ± 239 kg DM/ha throughout the grazing period. Supplementation did not influence (P> 0.10) ADG; overall, cows gained 0.47 ± 0.14 kg/d. Cows supplemented with SH (493 ± 25 kg) or CSB (485 ± 25 kg) had heavier (P<0.05) selling BW than control cows (462 ± 25 kg). Pregnancy rate tended (P=0.10) to be increased for cows receiving CSB (96%) compared with control cows (74%). Selling price of pregnant cows was increased (P<0.05) compared with non-pregnant cows. Supplementation of market cows increased selling BW but did not affect net income. Pregnancy rate tended to be increased in CSB cows, and selling price of pregnant market cows was greater than non-pregnant cows.

(Key Words: Market Cows, Stockpiled Fescue, Soybean Hulls, Pregnancy.)

Introduction Market beef cows account for 10 to 25% of the annual income of cowcalf production (Apple, 1999; Sawyer et al., 2004). Several studies have indicated that the feeding of market beef cows will increase carcass quality (Wooten et al., 1979; Cranwell et al., 1996; Schnell et al., 1997) and potentially increase net income (Apple, 1999). A recent survey of livestock auctions indicated that pregnancy status of replacement and market cows influenced their selling price (Troxel et al., 2002). Market cows often have thin body condition (Apple, 1999; Brown et al., 2003; Sawyer et al., 2004), and it is well established that decreased body condition hinders reproduction in cattle (Richards et al., 1989; Bossis et al., 1999). Thin cows have the potential to utilize energy

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and nitrogen more efficiently than fatter cows, resulting in compensatory gain (Freetly and Nienaber, 1998) and increased body condition (Matulis et al., 1987; Schnell et al., 1997). The feasibility of feeding market cows is largely dependent on feed costs (Rogers et al., 2004; Sawyer et al., 2004). Tall fescue is a commonly stockpiled cool-season forage because it provides sufficient forage growth and quality during winter months (Sleper and West, 1996; Hitz and Russell, 1998) and reduces winter feed costs approximately 60 to 75% when compared with conventional winter supplementation practices (BishopHurley and Kallenbach, 2001; Jennings et al., 2004). Forage digestion may be reduced by the supplemental energy source (Chase and Hibberd, 1987). Soybean hulls (SH), which are high in digestible fiber, have a more positive effect on forage intake and digestibility than corn-based supplements (Ovenell et al., 1991; Marston et al., 1993). Steers grazing stockpiled tall fescue and fed supplemental SH had increased ADG compared with steers grazing stockpiled fescue and fed supplemental corn (Burris et al., 2000; Larson et al., 2000). Increasing value of market cows with the intent of selling pregnant replacement cows has not been studied previously. Further, data are limited on BW and condition changes of cows supplemented with either starch- or fiber-based energy sources and grazing stockpiled tall fescue. The objective of this study was to determine the effect of supplementation on BW, BCS, ADG, pregnancy rate, selling price, and net income of market cows grazing stockpiled and spring-growth, endophyteinfected tall fescue.

Materials and Methods Forages. The experiment was conducted near Booneville (35° 5′′ N; 94° 0′ W) in west central Arkansas. Monthly precipitation data for the experiment site were collected during the 2 mo of stockpiling and during

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the months of grazing for both years (NOAA-NWS, 2004). To initiate the stockpiling process for tall fescue, pastures were clipped to a height of 10.2 cm and fertilized (October 1 in yr 1; September 26 in yr 2) with 40 kg N/ ha. Pastures were fertilized again in the spring (March 5 in yr 1; February 27 in yr 2) with 75 kg N/ha. Fescue pastures were characterized three times (initiation, mid point, and termination of grazing) during the experiment to determine forage availability and nutritive value. Forage availability was evaluated using a disk meter (Bransby et al., 1977). Forage height was recorded at 150 to 225 random locations (9 measurements/ha) in each pasture at the initiation, mid point, and at the termination of the experiment. To calibrate disk meter measurements, forage was clipped to ground level beneath the disk meter at five locations per pasture at the three sample periods. Samples were dried (60°C) in a forced-air oven for 72 h and weighed for calculation of regression equations of kg DM/ha and disk meter height. Random grab samples (20 samples/16 ha pasture) were utilized for evaluating nutritive value of forage at the three sample periods. Nutritive subsamples were ground to pass through a 2-mm screen and analyzed for CP (Kjeltech 1030 Auto Analyzer; Tecator, Hgans, Sweden), IVDMD, and ADF using the Goering and Van Soest (1970) procedure modified for use with the Ankom Daisy II In Vitro Digester威 (Ankom Technology Corp., Fairport, NY). Endophyte infection rates of tall fescue pastures were determined from tillers at 100 randomly selected sites in each pasture. Approximately 90% of the tillers in each pasture were producing ergot alkaloids (immunoblot detection method; Agrinostics Ltd. Co., Watkinsville, GA). Forage samples were clipped at ground level from 25 randomly selected sites in each pasture to determine concentrations of ergovaline at the three sample periods. Samples were pooled and dried (38°C) in a forced-air oven for 5 d; concentrations of ergovaline were

determined using HPLC as previously described (Craig et al., 1994). Cattle. All animal procedures were approved by the committee for animal welfare at the USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR. Seventy-five crossbred (≤¹⁄₄ Bos indicus), non-pregnant cows [age = 4.5 ± 0.2 yr; BW = 395 ± 10 kg; body condition score (BCS) = 4.3 ± 0.2, where 1 = emaciated to 9 = obese (Wagner et al., 1988)] were purchased by a cooperator at local auction barns in western and central Arkansas. Cows were vaccinated for Leptospirosis and Vibriosis (Vibrio-Lepto 5威; Biocor Animal Health Inc., Omaha, NE) and treated for internal and external parasites (Ivomec威 Plus, Merial Animal Health, Duluth, GA). Cows were randomly assigned to one of six pastures (two pastures per treatment each year) of stockpiled endophyte-infected tall fescue for 160 d (November 20 to April 29 for yr 1) or 147 d (December 2 to April 27 for yr 2) and continuously grazed with a fixed stocking rate of 1.25 cows/ha. In yr 1, five 16-ha and one 24-ha pastures were utilized, and four 16-ha, one 8-ha, and one 24-ha pastures were used in yr 2. Additional cows not utilized in this experiment grazed pastures simultaneously with market cows to obtain the desired stocking rate of 1.25 cows/ha. Cows were supplemented with either soybean hulls (SH; n = 24; CP = 10.6%; 1.5 NEm Mcal/d; DM basis) or corn:soybean meal (CSB; n = 24; 80% ground corn:20% soybean meal; 17.8% CP; 1.8 NEm Mcal/d; DM basis) or were not supplemented (n = 27; control). Supplements were fed at 0.91 kg/d per cow prorated to be fed 3 d/wk. Cows were offered a mineral premix (Pro-Phos 6 Mag威; Land O’Lakes, Shoreview, MN) ad libitum. Endophyte-infected tall fescue hay was supplemented when snow cover prevented grazing. Body weight and BCS were recorded monthly. Average daily gain was calculated with BW recorded at the initiation and termination of grazing. Cows were exposed to bulls (112

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d in yr 1; 98 d in yr 2) and palpated for pregnancy at the termination of the experiment. Cows were sold at a local auction (Waldron Livestock Auction, Waldron, AR) on May 8 (yr 1) and May 6 (yr 2), and selling price and BW were recorded. Statistical Analyses. Analysis of covariance was used to determine the effect of supplementation on BW, BCS, ADG, selling price, and net income of market cows using the MIXED procedure of SAS威 (SAS Inst. Inc., Cary, NC) with the model including the effects of replicate; year was used as a random effect. Initial BW and BCS were used as covariates. Utilizing pasture as the experimental unit limited the degrees of freedom for treatments (2 replications per treatment for 2 yr) in the current study; however, treatment was applied to cows within each pasture making the pasture the experimental unit (Fisher, 1999). The interaction of grazing period (initiation to mid point and mid point to termination) and supplementation was determined by the MIXED procedure of SAS. Forage availability and nutrient composition from the three sample periods were analyzed as repeated measures using the MIXED procedure of SAS with an unstructured covariance structure. Least squares means were compared using the PDIFF statement (Tukey’s) of SAS when protected by a significant (P<0.05) treatment effect. Chi-square analysis, using the FREQ procedure of SAS, was used to determine influence of supplementation on pregnancy rate of cows.

Results and Discussion Stockpiled Fescue Characteristics. Precipitation data were below the 30yr normal for both years during the 2 mo of stockpiling fescue prior to grazing (Table 1). Availability of forage was not affected (P>0.10) by treatment (data not shown) and averaged 3637 ± 239 kg DM/ha throughout the experiment (Table 2). Although a supplementation treatment effect on forage availability was not detected, methodologies used to estimate forage availability generally lack the accuracy and precision to detect small differences in availability among treatments, presumably affecting DMI (Aiken and Bransby, 1992). Forage availability was greater (P<0.05) at the initiation and termination of the experiment than at the mid point (Table 2). Cows were fed supplemental fescue hay (12 round bales; approximately 500 kg per bale) during yr 1 because of snow cover. Production of stockpiled fescue is influenced by initiation date (Poore et al., 2000). Yield of stockpiled fescue was 3110 kg DM/ha when stockpiling was initiated in September in North Carolina (Burns and Chamblee, 2000), 2370 kg DM/ha in Missouri (August initiation date; Kallenbach et al., 2003), and 2179 kg DM/ha in Arkansas when stockpiling was initiated in August (Jennings et al., 2004). In the current study, availability of stockpiled fescue decreased 38% from initiation of grazing (November 20 for yr 1; December 2 for yr 2) to the mid point of grazing (January 30 for yr 1;

February 3 for yr 2) probably because of animal consumption. Availability of stockpiled fescue declines from mid December through early winter in ungrazed pastures (Collins and Balasko, 1981a; Fribourg and Bell, 1984; Gerrish et al., 1994). Most tall fescue growth occurs during the cool months of the year with little or no growth during cold months (Fribourg and Bell, 1984; Ball et al., 2002). Forage intake increases as availability increases up to 2240 kg DM/ha (Martz et al., 1999). Forage availability was not limiting at any of the three sample periods in the current experiment. Crude protein and IVDMD were greater (P<0.05) at the initiation and termination of the experiment compared with the mid point (Table 2). Acid detergent fiber content was less (P<0.05) at the initiation of grazing compared with the mid point and termination sample periods (Table 2). Generally, CP percentage declines in stockpiled fescue from December through February (Collins and Balasko, 1981b; Fribourg and Bell, 1984; Kallenbach et al., 2003) while ADF remains stable or increases during cold periods (Fribourg and Bell, 1984; Kallenbach et al., 2003). An increased concentration of ADF at the mid point collection explains why IVDMD was reduced at the mid point, as ADF is negatively correlated with digestibility (Van Soest et al., 1978). Forage samples at the initiation (November and December) and termination (April) of the current experiment were collected during active growth of the plant, explaining the

TABLE 1. Monthly mean precipitation (cm) and 30-yr (1971–2000) normal precipitation during months of stockpiling tall fescue (September and October) and during months of grazing and feeding supplemental diets. Item

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

yr 1 yr 2 30-yr mean

6.4 4.9 10.3

8.0 0.4 9.9

2.4 1.0 12.9

16.3 7.4 10.8

0.5 3.7 8.2

11.6 7.8 7.8

5.1 9.0 10.3

5.8 15.6 11.0

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TABLE 2. Forage availability (kg DM/ha), CP, ADF, and IVDMD of stockpiled and spring-growth tall fescue. Item

Availability a

Initiation Mid pointb Terminationc SEM

x

4070 2509y 4333x 239

CP

ADF x

14.5 9.5y 13.7x 0.9

x

26.1 34.1y 36.6y 1.3

IVDMD 71.4x 46.5y 66.8x 4.8

a

November 20 for yr 1 and December 2 for yr 2. January 30 for yr 1 and February 3 for yr 2. c April 29 for yr 1 and April 27 for yr 2. x,y Sample period effect (P<0.05). b

greater CP and IVDMD percentages compared with the mid point sample (January and February). Mean concentrations of ergovaline ranged from 0.213 to 0.377 mg/kg DM during the experiment and were affected (P<0.05) by sample period (Figure 1). Concentrations of ergovaline at the initiation of stockpile grazing were 0.372 mg/kg DM, declined by 43% at the mid point, and then increased to approximately the same concentration as at the initiation by the final sampling. In Missouri, concentrations of ergovaline in stockpiled fescue were reduced 85% from December to March (Kallenbach et al., 2003). Cattle consuming stockpiled fescue in colder months may not be exposed to concentrations of ergovaline that induce fescue toxicosis (Stamm et al., 1994; Kallenbach et al., 2003). Tor-Agbidye et al. (2001) reported that dietary concentrations of ergovaline between 0.400 and 0.750

Figure 1. Concentrations of ergovaline of endophyte-infected stockpiled and springgrowth tall fescue at three sample periods during 2 yr. Sample period effect (P<0.05).

mg/kg DM may cause fescue toxicosis in cattle. Weight gain of beef steers was not affected by fescue straw containing up to 0.475 mg/kg DM of ergovaline (Stamm et al., 1994). Mean concentrations in the current study were less than these published values throughout the experiment. Individual cows may experience some degree of toxicosis at various times while grazing stockpiled and spring-growth, endophyte-infected tall fescue because of individual sensitivity. BW, BCS, and Pregnancy Rate of Market Cows. Average daily gain of market cows was increased (P<0.05) from the initiation to the mid point (0.77 ± 0.20 kg/d per cow) of grazing compared with ADG from the mid point to the termination (0.19 ± 0.07 kg/d per cow) of grazing among treatments. Similarly, market cows fed high concentrate diets were less efficient at feed conversion as days on feed increased (Schnell et al., 1997; Sawyer et al., 2004). Matulis et al. (1987) found market cows fed high concentrate diets for 84 d had increased ADG from d 29 to 56 compared with other time periods. Differences in ADG between grazing periods (initiation to mid point or mid point to termination) may be associated with compensatory gains up to the mid point of grazing with less gain efficiencies thereafter. Average daily gain of market cows throughout the experiment was similar (P>0.10) among cows supple-

mented with SH or CSB at 0.2% BW and non-supplemented, control cows (Table 3), and there was not (P>0.10) a supplementation × grazing period interaction. Overall, cows gained an average 73 ± 23 kg during the experiment. Forage digestion may be reduced by supplemental starch-based energy (Chase and Hibberd, 1987); however, energy supplements high in digestible fiber, such as SH, may alleviate these negative associative effects (Ovenell et al., 1991; Marston et al., 1993). Larson et al. (2000) found that calves grazing stockpiled tall fescue and fed supplemental SH (0.6% BW) had increased ADG compared with those calves grazing stockpiled fescue and fed supplemental cracked corn (0.6% BW). Differences in supplemental diets, forage quality, and experimental design may explain variations between the current study and previous research. The CP of the corn diet in the study of Larson et al. (2000) was 9%, while CP of the CSB diet in the current study was 17.8%. Further, nutritive content of pastures in the study of Larson et al. (2000) and the current study were different. The nutritive content of stockpiled tall fescue over 2 yr averaged 12.6% CP, 32.3% ADF, and 61.6% IVDMD in the current study. Utilizing the pasture as the experimental unit in the current study also limits the degrees of freedom and makes it more difficult to detect significant treatment differences (Fisher, 1999). The CP and TDN requirements of a 545-kg, mid gestation cow are 49% TDN and 6.9% CP (DM basis; NRC, 1984), indicating that if DMI was adequate, forage alone would have met the nutritional requirements of cows in the current study. Others have reported similar results of stockpiled tall fescue meeting or exceeding NRC nutritional requirements for beef cows (Collins and Balasko, 1981b; Kallenbach et al., 2003; Jennings et al., 2004). Quality of the stockpiled forage was apparently adequate to maintain BW and BCS of cows through the winter and early spring grazing period.

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TABLE 3. Influence of supplementation on selling BW and body condition score (BCS), BCS change, ADG, and pregnancy rate of market cows. Data are presented as least squares means.

Item Initial BW, kg Initial BCS Selling BW, kga Selling BCS BCS change ADG, kgb Pregnant, %

Control

Soybean hulls

Corn:soybean meal

SEM

398 4.1 462w 5.3w 1.0w 0.43w 74z

390 4.3 493x 5.7x 1.4x 0.51w 87yz

399 4.4 485x 5.6wx 1.3wx 0.47w 96y

10 0.2 25 0.2 0.2 0.3 —

a

Selling BW recorded at auction barn (May 8 in yr 1; May 6 in yr 2). Calculated with BW recorded at initiation and termination of grazing. w,x Means within a row with no common superscript differ (P<0.05). y,z Means within a row with no common superscript differ (P=0.10). b

Cows supplemented with either SH or CSB had increased (P<0.05) selling BW compared with non-supplemented control cows (Table 3). Selling BCS and BCS gain were greater (P<0.05) in SH cows compared with non-supplemented, control cows (Table 3). Market cows usually have low BCS and have the potential for compensatory BW gain (Freetly and Nienaber, 1998; Sawyer et al., 2004). Cows in the current experiment were thin (BCS = 4.3) at the initiation of the experiment, and SH cows had greater BCS (5.7) at the termination of the experiment. Fieser and Vanzant (2004) found SH supplied more digestible OM than cracked corn in steers fed fescue hay, independent of forage quality. Performance of market cows supplemented with SH was similar or greater than that of CSB cows in the current study. More cows supplemented with CSB in the current experiment tended (P= 0.10) to be pregnant than non-supplemented control cows (Table 3). To our knowledge, these are the first data on increasing the value of market cows by grazing stockpiled and spring-growth, endophyte-infected tall fescue with emphasis of selling pregnant, replacement cows. The majority of market cow research has in-

vestigated the effects of feeding high energy diets to market beef and dairy cows and harvesting carcass data (Apple et al., 1999; Funston et al., 2003). Thin body energy reserves are usually indicative of undernutrition, and it is well established that undernutrition hinders the reproductive process in cattle (Richards et al., 1989; Bossis et al., 1999). Market cows in the current study had a thin BCS (4.3) at purchase, and cows supplemented with SH had greater BCS at the termination of the experiment than non-supplemented cows. Although not statistically different, more supplemented cows became pregnant during the experiment than non-supplemented cows probably because of increased BCS. Further, the increased pregnancy of supplemented cows might have contributed to the increased selling BW of supplemented cows. Economics of Market Cows. Feed cost averaged $0.13/kg for SH ($18.43 per cow for each year) and $0.18/kg for CSB ($25.00 per cow for each year). Selling price of cows and net income were similar (P>0.10) among treatments (Table 4). Mean selling price was $667 ± $56 and net income was $75.30 ± $12 per cow among treatments. Pregnant market cows

had greater (P<0.05) selling prices than non-pregnant market cows ($694 ± $54 and $524 ± $58 for pregnant and non-pregnant cows, respectively). Supplementation of market cows grazing stockpiled and springgrowth tall fescue did not directly affect cow selling price or net income. However, more cows supplemented with CSB tended to be pregnant, and pregnant cows averaged $170 more than non-pregnant cows. Troxel et al. (2002) reported the selling price of replacement cows was more than the price of market cows. Further, replacement cows in the third trimester of pregnancy had the greatest price of all stages of pregnant replacement cows (Troxel et al., 2002). Market beef cows account for 10 to 25% of the annual income of cow-calf production (Apple, 1999; Sawyer et al., 2004). Beginning with healthy market cows is one of the most critical components in the success of adding value to market cows. In the current study, one cow died, and two cows were removed from the study because of health problems. Those data were not used in economic or performance analyses. Death losses of 1 to 2% have been reported in market cow studies (Brown et al., 2003; Sawyer et al., 2004). Data collected from 1995– 2004 by the USDA, National Agricultural Statistics Service (NASS, 2004) showed seasonal effects on the selling price of market beef cows. Prices generally are least during the months of November and December, and the greatest prices received for market cows are during March, April, and May. A majority (86%) of cows in the current study were pregnant and sold during May, allowing for greater selling prices relative to other times during the year.

Implications Nutritive content of stockpiled and spring-growth, endophyte-infected tall fescue exceeded the nutrient requirements of pregnant market cows. Further, concentrations of ergovaline did not exceed published values that

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a

TABLE 4. Means of costs , selling price, and net income associated with market cows grazing stockpiled and spring-growth tall fescue and fed supplemental diets.

Item

Control

Soybean hulls

Corn:soybean meal

Purchase price Feed cost Land leaseb Bull lease Labor costc Freight costd Miscellaneous coste Total cost Selling price Net income

396.13 0.0 12.34 20.00 9.90 10.00 108.57 556.94 640.05 83.11

412.79 18.43 12.34 20.00 29.70 10.00 108.57 611.83 674.21 62.38

401.38 25.00 12.34 20.00 29.70 10.00 108.57 606.99 687.40 80.41

SEM 19 — — — — — — — 56 12

a

In dollars on a per-cow basis. $37.05/ha per year with a stocking rate of 1.25/ha. c Labor cost assessed at $9.00/h. Feeding required 1 h, 3 d/wk for 22 wk for each supplemental treatment; control cows were observed once weekly (1 h for 22 wk). d Freight to and from auction barn. e Miscellaneous costs included fertilizer, hay fed during snow cover (yr 1), mineral premix, anthelmentics, and vaccinations. b

are associated with fescue toxicosis. Supplementation of market cows grazing stockpiled and spring-growth, endophyte-infected tall fescue tended to increase body condition and pregnancy rate, and pregnant market cows had greater selling prices compared with non-pregnant cows. Sale of pregnant market cows could be an additional source of income for cattle producers.

Acknowledgments The authors gratefully acknowledge L. Huddleston, USDA-ARS, for daily animal management; N. and T. Preston, Booneville, AR, for supplying cattle; and personnel at Waldron Livestock Auction, Inc., Waldron, AR, for collection of cattle sale data.

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