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ANIMAL PRODUCTION |
ARS, USDA, U.S. Meat Animal Research Center, Clay Center, NE 68933-0166
Abstract
Production data were collected on mature cows produced by mating Angus and Hereford (pooled AH), Brahman (Bh) and Boran (Br), and Tuli, a tropically adapted Bos taurus, sires by AI or natural service to Angus and Hereford cows. These cows were mated to Charolais bulls for the purpose of this study. Within each sire breed of cow, cows were assigned randomly to one of three feeding rates, 49 or 76 g of DMI/BW0.75 or ad libitum (10 to 12 cows/feeding rate group), with weekly individual animal feed consumption recorded. Lactation yields were recorded via the weigh-suckle-weigh protocol at approximately 14, 28, 56, 84, 112, 140, 168, and 196 d postpartum for each cow/calf pair. Means for milk yield at peak lactation, total milk yields, calf birth weight, age-adjusted weaning weights, preweaning daily gain, and feed efficiency were estimated. Peak yield (kg/d) for Bh (10.3 ± 0.36) was greater (P < 0.05) than for Tuli (9.0 ± 0.31). Total yield (kg, 212 d) for Bh (1802 ± 68) was greater (P < 0.05) than for Tuli (1532 ± 59). Birth weight of AH (44 ± 0.9) was heavier than for Bh and Br (P < 0.05). Preweaning daily calf gain (g/d) and adjusted weaning weight (kg) of Bh (813 ± 28, 212 ± 6.1) and Br (766 ± 24, 202 ± 5.1) differed (P < 0.05) from AH (589 ± 24, 169 ± 5.2) and Tuli (634 ± 24, 176 ± 5.3). Efficiency estimates (grams of adjusted weaning weight/kilograms DMI of the cow) for Bh (88 ± 2.5) and Br (85 ± 2.1) exceeded (P < 0.05) those for Tuli (74 ± 2.1) and AH (73 ± 2.1). Bos indicus breed crosses exhibited greater peak and total yield, lower birth weight, greater daily gain and adjusted weaning weight, and higher feed efficiency than did Bos taurus breed crosses (P < 0.05). Total yield, daily gain, adjusted weaning weight, and feed efficiency were higher (P < 0.05) for cows sired by bulls from tropically adapted breeds, and the peak yield was less (P < 0.10). Tuli exhibited lower total yield and birth weight than did Angus/Hereford (P < 0.05). The efficiency of crossbred Tuli cows did not differ from Angus/Hereford F1 females, but neither equaled the efficiency of crossbred cows produced using Bos indicus breeds.
Key Words: Adapted • Cattle • Efficiency • Preweaning • Sanga
Introduction
Diverse breed resources provide cow/calf producers with an opportunity to use breed combinations within defined production environments to meet product specifications for identified markets. Previous research documents the role of Bos indicus breeds of cattle for use in the cowherd in hot-humid production environments (Olson et al., 1991
; Brown et al., 2001). Green et al. (1991) reported more weight of calf weaned from F1 Bos indicus cows per unit of feed consumed by the cows from calving until weaning. Phillips et al. (2001) reported that calves whose dams were 50% Bos indicus exhibited greater weight gains on native prairie pastures during the stocking period than did straightbred calves. These positive contributions to beef production from Bos indicus breeds are offset by older ages at puberty (Gregory et al., 1979) and decreased meat tenderness with increasing percentage of Bos indicus breeding (Crouse et al., 1989).
Reproductive (Cundiff et al., 2000) and meat palatability potentials (Wheeler et al., 2001) of tropically adapted Bos taurus breeds of cattle may provide alternative breed resources for southern beef producers. Ferrell and Jenkins (1998) reported significant differences in body composition and energy utilization during the postweaning period for steers representing tropically adapted and unadapted breeds of cattle. These results document the need to characterize production characteristics of mature cows representing these diverse breed crosses of cattle.
The objective was to evaluate the abilities of tropically adapted Bos taurus and Bos indicus crossbred cows to convert feed resources to weight of calf weaned during the preweaning period relative to unadapted Bos taurus crossbred cows. Addressing this question for the period from calving through weaning may assist in identifying an alternative to Bos indicus for use as a maternal breed cross.
Materials and Methods
Animals and Management
Mature pregnant F1 (born from 1992 through 1994) cows were sampled from Cycle V of the Germ Plasm Evaluation Project. Angus, Hereford, Brahman and Boran (tropically adapted Bos indicus), and Tuli (tropically adapted Bos taurus) sires were mated by AI or natural service to Angus and Hereford cows. Mature cows from these matings were bred to Charolais sires. Those cows determined to be pregnant by rectal palpation from each sire breed of cow (SBC) group identified for use in the study were sampled. Within each sire of cow breed group, cows were randomly assigned to a diet at one of three feeding rates, 49 or 76 g of DMI/BW0.75 or ad libitum (10 to 12 cows/feeding rate group). Applied feeding rates were chosen to characterize production under marginal, adequate, and high DM availabilities. A cow’s daily rations were established using individual cow weights recorded upon entry into the testing area. Cows were housed in pens (three to four cows per pen, nine pens per SBC) in a concrete-floored, open-front barn with approximately 18.2 m2 of space per cow. Each pen was equipped with four electronic head gates. Sire breed of cow and feeding rate were confounded with pen. Cows failing to learn to use the electronic head gate were removed and were replaced when possible.
During the study, cows received corn silage plus soybean meal diet (DM basis; 2.60 Mcal of ME/kg of DM, 13% CP, an average of 38.6% DM) fed once daily with delivered amounts recorded. Samples were taken weekly during the study for DM determination. Feed refusals were collected, weighed, and recorded weekly. Male calves were castrated at birth. During the testing period, calves were limited to a weekly presentation of 2 to 3 kg (as-fed basis) per calf of a creep feed consisting of corn silage and ground alfalfa hay, beginning when the oldest calf within a pen was 110 d of age. Other than this creep feed, the dam’s milk production was the sole source of nutrients for the calves. All calves were weaned and weights recorded at an approximate mean age of 210 d.
Calving began approximately the second week in March and continued through the third week in May (average birth date March 22). At approximately 14, 28, 56, 84, 112, 140, 168, and 192 d postpartum, milk production measurements were recorded using a weigh-suckle-weigh technique for each cow/calf pair (Totusek, 1973). Calves were separated from their dam for an 18-h period preceding the measurement. Differences between pre- and postsuckle calf weights were recorded as milk production measurement for that day. Individual cow measurements were used to estimate lactation curve parameters (Y[n] = n(aekn)–1; Jenkins and Ferrell, 1992), which were used to predict time of peak lactation, yield at time of peak lactation, and total milk yield of lactation, persistency, and yield on the last day of lactation (Jenkins et al., 2000). Research protocols followed the guidelines stated in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 1999) and were approved by an Institutional Animal Care and Use Committee (IACUC No. 47-F-002).
Statistical Analyses
Analyses of covariance (Steele and Torrie, 1960) were used to partition variation associated with the fixed effect of SBC, random effect of sire within SBC, and the covariate adjusted total DMI (adjusted to 212 d of intake) using the GLM procedure in SAS (SAS Inst., Inc., Cary, NC). Where appropriate, sex of calf was included as a fixed effect. Initial models included linear and quadratic terms for total adjusted DMI and potential interactions. Differences in performance between Bos taurus vs. Bos indicus, tropically adapted vs. unadapted, and Bos taurus unadapted vs. Bos taurus adapted cows were determined using linear contrast.
Response variables include the lactation traits predicted from parameters estimated from individual cow’s milk production by fitting the data to a lactation model reported by Jenkins and Ferrell (1992). Parameters from the solution of this model were used to calculate the response traits of time and yield at peak lactation (PY) and total yield (TY) for each cow. Persistency and yield on the last day of lactation were calculated from model parameter estimates. Persistency is defined as the difference between yield last day of lactation and yield at time of peak lactation relative to the number of days between the two events (Jenkins et al., 2000). Calf traits included birth weight, weaning weight adjusted to 212 d (AWW), preweaning daily gain (DG; [AWW – BW]/212), and feed efficiency (EF; g of calf weight weaned/kg of DMI of dam). Initial models included SBC, pooled linear and quadratic terms for daily ME intake, these effects interacted with SBC, and calf gender. The random effect of sire within SBC was used as the error term for SBC where appropriate.
Results and Discussion
Preliminary analyses indicated no significant differences in performance between cows produced by Angus or Hereford sires. These two SBC groups were pooled in the remaining analyses. Simple means and CV for production traits of interest are reported in Table 1. Initial cow BW and body condition scores (1 to 9 scale, with 1 indicating extremely low body fat, and 9 indicating extremely high body fat) were recorded approximately 8 to 10 wk after weaning of the previous year’s calf (Herd and Sprott, 1986). Individual initial cow BW provided the basis upon which to establish daily rations. Dry matter intakes are shown in Table 1. Mean cow heights measured at the hooks and weaning age by breed and rate of feeding are reported.
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. The random effect of sire within SBC approached significance (P < 0.09) for total milk yield and was significant (P < 0.05) for yield on the last day of lactation and time of peak yield. The effect of sire within SBC served as the error term to test the effect of SBC for these three traits. Time of peak lactation (approximately 10 wk after parturition) was not affected by SBC, DMI, or sex of calf. The remaining effects in the model and SBC for the remaining lactation traits were tested against residual error. Sire breed of cow effect was significant for peak yield and total yield. Neither the linear nor quadratic effects of DMI were significant for any of the lactation traits. The effect of sex of calf on peak and total milk yield and persistency tended to differ (P < 0.10) for steer (10 ± 0.2 kg, 1,718 ± 43 kg, –0.039 ± 0.001 kg/d) and heifer (9.6 ± 0.2 kg, 1,651 ± 44 kg, –0.036 ± 0.001 kg/d) calves.
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) for preweaning gain (P < 0.08) and efficiency (P < 0.09). Sire breed of cow differences were tested using this factor as the error. Remaining effects in the model were tested against residual error, as was SBC for birth weight and age-adjusted weaning weight. Significant SBC differences were noted for all traits. The linear effect of DMI was not significant on birth weight but was highly significant for the other traits. Gain was not affected by sex of calf but birth weight (P < 0.01), adjusted weaning weight, and efficiency (P < 0.07) were greater for steer (42.6 ± 0.7 kg, 193 ± 3.7 kg, 86 ± 1.6 g/kg of DMI) than for heifer (40 ± 0.7, 185 ± 3.8 kg, 82 ± 1.7 g/kg) calves. Estimates of the pooled regression coefficients of DMI for preweaning daily gain (g/d), age-adjusted weaning weight (kg) and efficiency (grams of calf gain/kilogram of cow DMI) were 0.093 ± 0.026, 0.021 ± 0.005, and –0.022 ± 0.002; respectively.
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. The peak yield of Angus/Hereford-, Brahman-, and Boran-sired cows was similar, with the Angus/Hereford and Brahman peak milk yields exceeding those of Tuli (P < 0.05). Peak yields of the Boran- and Tuli-sired cows were similar. Similar numerical rankings and significance difference patterns were observed for 212-d total yield.
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). Ferrell (1991) provided evidence that fetal growth of either Charolais or Brahman fetuses from 232 d after conception to 271 d was restricted by the Brahman maternal environment when compared with Charolais or Brahman fetuses developing in a Charolais maternal environment. Preweaning ADG and age-adjusted weaning weights for Brahman and Boran SBC groups exceeded (P < 0.05) the Angus/Hereford and Tuli SBC. Efficiency was defined as the ratio of age-adjusted preweaning weight gain of a calf relative to total DMI of the cow during the preweaning period and was expressed as grams of weight change per kilogram of DMI. Total DMI was adjusted to the mean weaning age of 212 d. Brahman and Boran SBCs were more effective (P < 0.05) in converting DM to calf weight gain than were Angus/Hereford and Tuli SBC groups.
Factors enhancing cow/calf productivity of Bos indicus crossbred cows in the production environment characterized as hot and humid are documented (Turner, 1980). Koger (1980) described crossbreeding systems to effectively capture the benefits of tropically adapted cattle. Crouse et al. (1987) reported less desirable carcass and palatability attributes as the proportion of Bos indicus breeding increased. Because of this negative relationship, easily observed phenotypic characteristics associated with Zebu-derived cattle are used to discriminate against these breed crosses in the marketplace (Sherbeck et al., 1996). Results such as these continue to promote interest in the potential of tropically adopted Bos taurus as a breed resource to replace Bos indicus in crossbreeding systems.
Variation between groupings of SBC, tropically adapted vs. unadapted SBC, Bos indicus and tropically adapted Bos taurus SBC, and tropically adapted vs. unadapted Bos taurus was partitioned with linear contrast to test if productivity for traits of interest between comparisons was similar (Table 5). Bos indicus-sired cows tended (P < 0.07) to have higher yields at time of peak lactation and had greater total yields (P < 0.01) than Bos taurus-sired cows. Preweaning gain and age-adjusted weaning weights of calves of Bos indicus-sired cows were greater (P < 0.01) than the same traits for Bos taurus-sired cows; however, BW was heavier (P < 0.01) for Bos taurus-sired cows than for Bos indicus-sired cows. Bos indicus-sired cows were more effective (P < 0.01) in converting feed energy to calf weight during the preweaning period than were Bos taurus-sired cows.
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provided information from a larger sample, reporting minor differences in BW among SBC, and a ranking of Brahman (211 kg), Boran (201 kg), Angus/Hereford (194 kg), and Tuli (187 kg) for weaning weights at 200 d. Direct comparison of production traits for tropically adapted (Tuli) and unadapted Bos taurus (Angus/Hereford)-sired cows indicate that the tropically adapted cows had lower peak yields (P < 0.05) and tended to have lower total lactation yields than did the unadapted Angus/Hereford SBC. No differences were observed between these two SBC for the remaining traits.
Production characteristics associated with weaned calf enterprises were compared for mature cows produced by mating Angus or Hereford cows to Angus/Hereford, Brahman, Boran, and Tuli sires. Lactation measures, calf growth characteristics, and efficiency of the tropically adapted Bos indicus were greater than those of the Bos taurus, which supports previous research regarding the productivity of the Bos indicus crossbred cow. Measures of productivity for Tuli-sired cows in the present study were similar to those of Angus/Hereford-sired females. Evaluation of carcass tenderness attributes (Wheeler et al., 2001) among these SBC revealed higher tenderness (lower shear force) values for Tuli-sired calves relative to either Brahman- or Boran-sired calves. These results suggest the Tuli breed may represent a viable alternative to Angus/Hereford crossbred cows for use as a maternal breed cross in production environments where a tropically adapted germplasm is needed. However, the production efficiency of F1 cows derived from Bos indicus germplasm exceeded that of the Tuli F1 cows in the present study.
Implications
Commercial cow-calf producers whose enterprises are located in hot and humid areas need access to tropically adapted breeds or breed crosses. Crossbred cows containing Bos indicus germplasm are prevalent in these areas. Calves from these cows are frequently discounted at the market because of perceived problems with carcass tenderness. A need exists to identify tropically adapted breed resources, characterized as having acceptable carcass tenderness, to substitute for Bos indicus. The weaned calf production of mature F1 Tuli was comparable to F1 Angus/Hereford females. Neither breed cross was equal in performance to the Bos indicus tropically adapted breeds. The Tuli may represent a viable alternative to Bos indicus breeds for use as a maternal breed cross to decrease the potential loss in meat quality attributes sometimes found in progeny from maternal breed crosses containing Bos indicus germplasm but at a cost to cow herd performance relative to the Bos indicus crossbred cows.
Footnotes
1 Mention of a trade name, proprietary product, or specified equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. 
2 Correspondence: P.O. Box 166 (phone: 402-762-4247; fax: 402-762-4173; e-mail: jenkins{at}email.marc.usda.gov).
Received for publication December 12, 2003. Accepted for publication February 23, 2004.
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