Effects of 84-, 112- and 140-day postweaning feedlot performance tests for beef bulls

Changes in performance traits in beef cattle over the last 30 yr necessitate the re-evaluation of central testing procedures to ensure that they are cost effective and appropriate for current test objectives. The objective of this study was to evaluate the potential for reducing the length of evaluation from 140 d to either 112 or 84 d. Data evaluated were postweaning feedlot performance test records (collected from 1977 to 1986) on 1,830 individually fed bulls. Bulls representing 13 breeds (n greater than 25 per breed) were evaluated in the University of Arkansas Cooperative Bull Tests at Fayetteville, Hope, and Monticello, Arkansas. Models were fit for ADG, daily feed intake (FI) and feed conversion (FCONV) from d 1 to d 140 (ADG1-140, FI1-140 and FCONV1-140, respectively) and from d 1 to d 112 (ADG1-112, F11-112 and FCONV1-112, respectively). Models fit for ADG1-140, FI1-140, and FCONV1-140 using information up to d 112 had R2 of .90, .99, .88, and .94, respectively, and using information up to d 84 had R2 of .82, .94, and .80, respectively. Spearman rank correlation coefficients (all P less than .0001) were .93 for ADG1-140 and ADG1-112, .93 for ADG1-112 and ADG1-84, .99 for FI1-140 and FI1-112, .91 for FCONV1-140 and FCONV1-112, and .90 for FCONV1-112 and FCONV1-84. These coefficients indicate that bulls ranked similarly for performance traits at 84, 112, and 140 d. If the primary objective of central station testing is to evaluate ADG during the linear phase of growth, and if testing procedures are those currently recommended by the Beef Improvement Federation, then feeding bulls beyond 112 d has no advantage because the information upon which selection decisions are made is similar at both 112 and 140 d.     

Genetic correlations between test station and on-farm performance for growth rate and backfat in pigs

Record of performance data taken on Yorkshire pigs on-farm in 123 breeder herds and at a central test station were used to estimate genetic correlations between measures of backfat depth and days to 90 kg on boars at the test station and boars and gilts on-farm. The data involved records on 3,513 station-tested boars, 13,760 farm-tested boars and 28,203 farm-tested gilts from 838, 2,098 and 2,339 sires, respectively. For backfat depth, estimates of genetic correlations were .85 for test station and on-farm boars and 1.04 for test station boars and on-farm gilts. Estimates of genetic correlations between test station and on-farm measures of days to 90 kg were .80 for boars and .74 for boars and gilts. Based on these results, selection of boars on the basis of test station performance for backfat and growth rate would be expected to result in genetic improvement on-farm in both sexes under North American testing and management conditions.     

Effect of pre-weaning selection on estimates of genetic parameters and breeding values for post-weaning growth rate of beef bulls on test

Data on South African Angus cattle consisting of 45 259 records on weaning weight (WWT), 4 360 records on average daily gain from on-farm test (ADG-D) and 1 118 from centralized test (ADG-C) were analyzed to evaluate the effect of pre-weaning selection on estimates of genetic parameters and subsequent estimated breeding values (EBV) for post-weaning average daily gain. (Co)variance components and genetic parameters for weaning weight (WWT), ADG-C and ADG-D were estimated by REML procedures fitting three different animal models. Model 1 was a univariate model of WWT, ADG-C or ADG-D and did not account for the effect of pre-weaning selection on post-weaning ADG. Model 2 was a two-trait model of WWT and either ADG-C or ADG-D. Model 3 was a multi-trait animal model including WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39 ± 0.080, 0.42 ± 0.060 and 0.44 ± 0.010 from Model 1, 2 and 3 respectively. Corresponding estimates for ADG-D were 0.18 ± 0.020, 0.19 ± 0.020 and 0.21 ± 0.020 respectively. Rank correlations based on EBVs for ADG-C for all bulls were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3, and Model 2 vs. Model 3, respectively and they indicated a possible re-ranking of bulls when including or excluding a correlated pre-weaning trait. Rank correlations for ADG-D also followed a similar trend. Inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning.     

Genetic associations between feed efficiency measured in a performance test station and performance of growing cattle in commercial beef herds

Interest in selection for improved feed efficiency is increasing, but before any steps are taken toward selecting for feed efficiency, correlations with other economically important traits must first be quantified. The objective of this study was to quantify the genetic associations between feed efficiency measured during performance testing and linear type traits, BW, live animal value, and carcass traits recorded in commercial herds. Feed efficiency data were available on 2,605 bulls from 1 performance test station. There were between 10,384 and 93,442 performance records on type traits, BW, animal value, or carcass traits from 17,225 commercial herds. (Co)variance components were estimated using linear mixed animal models. Genetic correlations between the muscular type traits in commercial animals and feed conversion ratio (-0.33 to -0.25), residual feed intake (RFI; -0.33 to -0.22), and residual BW gain (RG; 0.24 to 0.27) suggest that selection for improved feed efficiency should increase muscling. This is further evidenced by the genetic correlations between carcass conformation of commercial animals and feed conversion ratio (-0.46), RFI (-0.37), and residual BW gain (0.35) measured in performance-tested animals. Furthermore, the genetic correlations between RFI and both ultrasonic fat depth and carcass fat score (0.39 and 0.33, respectively) indicated that selection for improved RFI will result in leaner animals. It can be concluded from the genetic correlations estimated in this study that selection for feed efficiency will have no unfavorable effects on the performance traits measured in this study and will actually lead to an improvement in performance for some traits, such as muscularity, animal price, and carcass conformation. Conversely, this suggests that genetic selection for traits such as carcass quality, muscling traits, and animal value might also be indirectly selecting for more efficient animals.     

Influence of growth rate and exposure to bulls on age at puberty in beef heifers

Two experiments were conducted to test the following hypotheses: 1) exposure of beef heifers to sterile bulls increases the proportion of heifers attaining puberty by 14 mo of age and 2) rate of growth interacts with bull exposure to influence age at puberty in beef heifers. In Exp. I, heifers were assigned to one of two treatments: 1) heifers were exposed to bulls (BE; approximately 70-d period of exposure) or 2) heifers were isolated from bulls (NE) and served as controls. In Exp. II, heifers were assigned to either BE or NE treatments (175-d period of exposure to bulls) and were fed to gain at a moderate (MG; .6 kg/d) or high (HG; .8 kg/d) growth rate. Blood samples were collected twice weekly to determine concentrations of progesterone indicative of onset of corpus luteum function and puberty. In Exp. I a greater (P less than .05) proportion of heifers receiving the BE treatment than of heifers receiving the NE treatment initiated corpus luteum function by 14 mo of age. In Exp. II, there was a bull exposure x growth rate interaction (P less than .05). The effect of bull exposure was greater within the HG groups than within the MG groups. However, heifers fed to attain a moderate or high growth rate and exposed to bulls attained puberty at younger ages than heifers not exposed to bulls and fed to attain a moderate or high growth rate. Mean ages at puberty were 375, 422, 428, and 449 (pooled SEM = 8.6) d for heifers in the BE-HG, BE-MG, NE-HG, and NE-MG groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term supplementation of lasalocid-sodium for beef bulls during grazing and subsequent finishing period

117 white-red beef bulls were involved to investigate the effect of lasalocid-sodium when fed either during the grazing period, or the finishing period, or during both subsequent periods. The ionophore was fed at 250 mg daily per head incorporated in 1 kg dry sugar beet pulp on pasture and at 65 mg per kg concentrate afterwards (corresponding with 27 ppm in the ration DM). The finishing diet consisted of maize silage ad libitum and 0.75 kg concentrate per 100 kg liveweight per day. On pasture lasalocid significantly increased daily gain form 0.6 to more than 0.7 kg, without affecting the grazed area per animal. During the finishing period growth rate was only slightly affected by lasalocid, but feed intake was reduced (P less than 0.05) and feed conversion improved (P less than 0.05). Feeding lasalocid permanently for more than 400 days did not reduce these positive effects. Cumulative daily gain, total feed intake per head and feed conversion were 1.12 kg, 2176 kg dry matter (DM) and 4.70 kg DM. These figures amounted to 1.05 kg, 2283 kg DM and 5.16 kg DM when no lasalocid was fed; 1.06 kg, 2141 kg DM and 4.87 kg DM when lasalocid was only fed during the finishing period and 1.09 kg, 2246 DM and 4.99 kg DM when lasalocid was only fed during the grazing period. Daily gains of 1.05 and 1.06 kg were significantly lower (P less than 0.05) than 1.12 kg. Most carcass data were unaffected, except fatness. The permanent feeding of lasalocid increased carcass fatness, mainly as the result of a higher final weight.     

Associations between viral infection and respiratory disease in young beef bulls

Blood samples were taken from bull calves at two Meat and Livestock Commission performance testing centres, just after weaning at six months of age and at six weekly intervals until the end of the performance test seven months later. Sera were assayed by specific ELISAS for antibodies to bovine herpes virus 1 (BHV1), respiratory syncytial virus, parainfluenza 3 (Pi3) and adenoviruses A and B. Seroconversions between each sampling were related to the occurrence of clinical respiratory disease using chi-squared (chi 2) and relative risk (RR) analyses. In 294 bulls there were 123 cases of respiratory disease. Seroconversion to bovine respiratory syncytial virus (RR = 4.7, chi 2 = 96.3, P less than 0.001) and adenovirus A (RR = 1.8, chi 2 = 8.9, P less than 0.001) and adenovirus B (RR = 1.9, chi 2 = 5.6, P less than 0.05) were significantly associated with clinical respiratory disease. There was evidence that prior exposure to respiratory syncytial virus (RR = 0.4, chi 2 = 9.8, P less than 0.01) Pi3 (RR = 0.4, chi 2 = 12.8, P less than 0.01) and adenovirus A (RR = 0.7, chi 2 = 7.5, P less than 0.01) conferred some protection against respiratory disease after arrival at the centre. It is concluded that vaccination before weaning, at least against bovine respiratory syncytial virus, would be beneficial.     

Heritabilities and genetic correlations for postweaning growth and feed intake of beef bulls and steers

Data from studies conducted at Miles City, MT and Lethbridge, AB were pooled to evaluate genetic and environmental variation in feed intake (MEI), growth rate (ADG), MEI-to-gain ratio (M/G), final weight (FWT), and fat thickness (FAT). A total of 124 sires with an average of 4.25 progeny each were represented in the data. Restricted maximum likelihood methods were used to estimate within and between paternal half-sib estimates of variance and covariance. Heritabilities and genetic, phenotypic, and environmental correlations with inference to populations at 365 d of age were calculated from the estimates. Heritabilities were as follows: ADG, .38 +/- .16; MEI, .45 +/- .17; M/G, .26 +/- .15; FWT .25 +/- .15; and FAT .52 +/- .17. The genetic correlation of MEI with ADG was large (.73 +/- .13) and antagonistic to genetic improvement of M/G through selection for ADG. Efficient genetic improvement in M/G was found to depend on using either MEI or an indicator of composition of gain as selection criteria in addition to ADG. Selection to improve M/G using an index that included FWT and FAT, in addition to MEI and ADG, resulted in greater predicted response in ADG and lesser predicted response in MEI than the index of ADG and MEI alone.     

Bayesian estimation of Tritrichomonas foetus diagnostic test sensitivity and specificity in range beef bulls

Accuracy of culture for diagnosis of Tritrichomonas foetus was investigated in 2832 naturally exposed range beef bulls from 124 herds. Preputial fluid samples were inoculated into the culture medium, incubated at 37 degrees C, and daily examined. Diagnostic test was evaluated using Bayesian techniques to estimate sensitivity and specificity without a gold standard. Median posterior test sensitivity was 72.04% (95% probability interval: 58.07-86.38%) and specificity was 95.37% (95% probability interval: 94.07-96.65%). Low diagnostic test accuracy may have resulted from host and/or diagnostic test procedure related factors. Under natural range conditions, more accurate methods for T. foetus diagnostic and repeated preputial samplings of bulls may be necessary on trichomonosis control programs.     

Relationship between serving capacity of beef bulls as predicted by the yard test and their fertility during paddock mating

Six experiments were conducted to determine the relationship between the serving capacity of bulls as predicted by a 40-min yard test and their fertility during paddock mating, measured by the conception rate at first oestrus and the pregnancy rate at the end of 10 weeks of mating. Twenty bulls varying in serving capacity from 1 to 11 were mated to 40 heifers each. As serving capacity of the bulls increased from 1 to 7, conception rate increased from 18 to 70%. Average conception rates achieved by 4 bulls with low serving capacity (25.3%), 8 bulls with medium serving capacity (61.4%) and 7 bulls with high serving capacity (72.3%) were all significantly different from one another. Bulls of low serving capacity (1 or 2 services) impregnated a significantly lower proportion of their heifers (40.3%) than bulls with medium (91.2%) or high (95.3%) serving capacity. It was concluded that bulls of serving capacity 1 or 2 (in 40 min) should be considered unsound for breeding. An explanation for the results and their implication in beef production is discussed.     

Herd and within-herd BoHV-1 prevalence among Irish beef herds submitting bulls for entry to a performance testing station

Infectious bovine rhinotracheitis (IBR), caused by bovine herpes virus 1 (BoHV-1), may result in various clinical consequences, including severe respiratory disease and conjunctivitis, venereal disease and reduced reproductive performance and abortion. This paper presents the serosurveillance findings from an intake of bulls into a performance testing station in Ireland during November 2007. The herd and within-herd BoHV-1 prevalence in 53 Irish beef herds and the risk factors for infection in these herds were determined, among bulls entering a beef performance testing station in Ireland. BoHV-1 status was determined for 41 herds, of which 30 (73.2%) herds were infected and the mean within-herd BoHV-1 prevalence was 28 (± 20)%. Multivariate exact logistic modelling revealed increasing numbers of contiguous herds and decreasing percentage of males within the herd as significant risk factors associated with infected herds. These findings highlight the high prevalence of BoHV-1 infection in those Irish beef herds that submitted bulls to this performance testing station, and raise concerns regarding IBR control nationally.     

Genetic associations between temperament and performance traits in Nellore beef cattle

The aim of this study was to estimate genetic associations between temperament and performance traits. Temperament was evaluated in yearling male and female Nellore cattle, using four traits: temperament score (TS), for assessing animals’ reactions in a corral pen (n = 25 691); movement score (MOV), for animals’ movements recorded inside the crush; crush score (CS), for animal's general reactivity inside the crush; and flight speed (FS), for the speed (in m/s) at which the animals exited the crush (n = 11 697, for the last three methods); for all the temperament traits, lower scores indicate animals with calmer temperament. Performance traits were visual scores for conformation (C), finishing precocity (P) and muscling (M) evaluated at yearlings, and average daily gain (ADG) was estimated from weaning to yearling. Bayesian inference using Gibbs sampling was applied to estimate (co)variance components and genetic and phenotypic parameters. Heritability estimates for the temperament traits ranged from 0.07 (CS) to 0.28 (FS). Genetic correlations of the temperament traits with ADG and C, P and M were negative and ranged from −0.02 to −0.31. Phenotypic correlations were negative and consistently lower than the genetic, ranging from −0.08 to −0.02. It was concluded that the temperament traits assessed had favourable genetic correlation estimates with the performance traits studied. However, indirect responses in temperament when selecting for higher ADG and visual scoring system of C, P and M, will be low.     

Scrotal circumference adjustment factors for age and weight differences in beef bulls

Scrotal circumference measurements were analyzed to develop appropriate adjustment factors for age and body weight differences in beef bulls. Age, body weight, and scrotal circumference measurements were collected on 863 Angus, 753 Polled Hereford, and 302 Simmental bulls from the Missouri tested bull sale, 1169 Polled Hereford bulls from the American Polled Hereford Association, and 465 Polled Hereford and 264 Simmental bulls from Nichols Farms in Bridgewater, Iowa. Within sources, data were subdivided into appropriate subsets and then each subset was statistically analyzed. Adjustment factors to remove differences in scrotal circumference due to age and body weight were developed for bulls of each of the 3 breeds studied.     

Associations between sperm abnormalities, breed, age, and scrotal circumference in beef bulls

The objectives of this study were to determine the associations of breed, age, and scrotal circumference (SC), and their interaction, on the prevalence of sperm abnormalities in beef bulls in Alberta, Canada, and the percentage of satisfactory potential breeders identified during breeding soundness examination solely due to normal sperm morphology. Eosin-nigrosin stained semen smears and evaluation reports of 1642 bull breeding soundness evaluations were procured from 6 veterinary clinics in Alberta. Sperm morphology was determined for at least 100 sperm per bull. The most common defects were detached head [4.86% ± 5.71%; mean ± standard deviation (s)], distal midpiece reflex (6.19% ± 9.13%), and bent tail (1.01% ± 1.54%). Although breed, age, and SC did not significantly affect the prevalence of head or midpiece defects, morphologically normal or abnormal sperm, tail defects were more prevalent in Angus and Hereford bulls compared with other breeds. Overall, solely on the basis of sperm morphology, 1363 (83.0%) bulls were classified as satisfactory potential breeders and the remainder 279 (17.0%) as unsatisfactory (> 30% abnormal sperm, > 20% defective heads, or both). Although not significantly different, the breed with the highest percentage of satisfactory potential breeders was Limousin (90.6%) and the lowest was Hereford (78.8%). That 17% of bulls subjected to breeding soundness evaluation were designated as unsatisfactory solely on the basis of sperm morphology highlights its importance.     

Comparison of methods for predicting yearling scrotal circumference and correlations of scrotal circumference to growth traits in beef bulls

From 1981 through 1986, BW, hip height, and scrotal circumference (SC) measurements were obtained on 329 bulls at the start of a 140-d gain test (SOT) and every 28 d to the end of test (EOT). Age, overall ADG, weight per day of age, ADG by period, and SC growth (cm/d) were calculated. Data were analyzed in two data sets because age of dam (AOD) and birth weights were unavailable between 1981 and 1983. Correlations of SC to other traits measured and probabilities for bulls attaining 30 or 32 cm SC by 365 d of age were calculated. Two adjusted 365-d SC (365-d SC) were calculated for each individual from regression analysis and from the following formula: 365-d SC = [(SCEOT-SCSOT)/140 d] x [365-ageSOT] + SCSOT. Except for ADG in Data Set 2, breed group differences (P less than .05) were observed for correlations of SC to all growth traits, age, and AOD. To attain 30 cm SC by 365 d of age with nearly 100% probability, Angus, Simmental and Zebu-derived bulls needed a 23-cm SCSOT, whereas continental (other than Simmental) and Polled Hereford bulls required a 26-cm SCSOT. Overall, 365-d SC means calculated by regression analysis or formula method did not differ (P greater than .10) for either data set.     

Horses' behavior and heart rate in a preference test for shorter and longer riding bouts

A Y-maze preference test was used to investigate whether horses prefer a shorter riding treatment over a longer riding treatment. In a pilot study (n = 4 horses), the maze was positioned with the 2 arms each pointing toward one of the short sides of the indoor arena, and in the main study (n = 14), the maze was rotated by 90°. Horses were 11 ± 4.4 years old and ridden regularly for at least 5 times/wk. They were conditioned to associate 1 exit of the maze with 1 lap of riding (R1), covering a distance of approximately 40 m at the walk or trot according to a predetermined schedule, and the other exit with 2 such laps (R2). Immediately afterward, riders dismounted, horses were led into the maze, and horses were let loose to make their choice in the maze. After exiting the maze, the rider mounted again and rode according to the chosen treatment. This procedure was repeated on the same day until statistical significance (P < 0.05) of preference was reached or up to a maximum of 35 trials. In addition, behavioral observations and heart rates were recorded. In the pilot study, all horses, regardless of the associated treatment, chose the left arm, which, unfortunately, pointed toward the arena's exit door. If horses were not caught immediately after exiting the maze (n = 5 occasions), they walked or trotted straight to the door. In the main study, 4 horses significantly preferred R1, 2 horses significantly preferred R2, and 8 horses had no significant preference. Heart rates were significantly (P < 0.05) higher during R2 (87.4 ± 2.6 bpm) than during R1 (79.5 ± 2.4 bpm). Except for tail swishing, no significant differences were found for the frequency of occurrence of behavior patterns between R1 and R2. Over the course of repeated trials, some horses became increasingly reluctant to enter and walk through the maze, and most showed increasing resistance to being remounted (e.g., sidestepping). Overall, the experimental setup did not seem to be appropriate to answer the research question. It is likely that the repeated mounting and dismounting caused discomfort or confused many of the horses to an extent that they did not actively select a treatment but rather searched for ways to evade further mounting (and riding). In conclusion, horses did not show a clear preference for either shorter or longer riding bouts, but their behavioral reactions indicate that they perceived mounting as uncomfortable and that their motivation to rejoin their herd-mates and/or to obtain feed in the barn was greater than their motivation to being ridden at all. Nevertheless, pronounced individual differences also seem to exist, with some horses showing little aversion to, and perhaps enjoyment of, being ridden, whereas others clearly preferring not to be ridden.     

The relationship between scrotal circumference at weaning and at one year of age in beef bulls

Scrotal circumference data obtained from performance test station bulls were corrected to 240 and 365 days of age. Data were analyzed, retrospectively, to determine the outcome for scrotal circumference at 365 days of age, if bulls were culled at selected cut-off values for scrotal circumference at 240 days of age. The data indicate that scrotal circumference measurements in weaned bulls may not be useful as a culling tool, since a large proportion of bulls, irrespective of breed, fell below the selected cut-off measurement for scrotal circumference at weaning, but met the minimum scrotal circumference at one year of age. Scrotal circumference measurements at 240 days of age may, however, be useful as a tool for selecting bulls with a greater than 80% probability of achieving the minimum scrotal circumference measurement at one year of age.     

Statistical associations between restriction fragment length polymorphisms and quantitative traits in beef cattle.

Data on 41 traits from 677 animals produced in a five-breed diallel were matched with genotypes for five marker-loci provided by restriction fragment length polymorphisms to detect quantitative effects associated with the markers, following three different designs based on inbred lines, half-sib families, and on assumptions of the markers being quantitative trait loci (QTL). Three growth hormone-TaqI alleles, B, C, and D, in high frequencies in this sample of the Brahman breed, were associated with decreases in birth weight, as a maternal trait (P < .01), and decreases in shoulder width at birth (P < .05). Among F2 Angus-Brahman and Brahman-Hereford cows, homozygotes for the B, C, or D alleles gave birth to calves 4.0 kg lighter than cows homozygous for the A allele, an effect that amounts to the magnitude of the corresponding breed difference in the diallel, and represents one phenotypic SD. A putative cytoplasmic effect seems to interact (P = .02) with this effect on maternal birth weight. Also, at birth, F2 calves homozygous for the B, C, or D alleles were .8 cm narrower at the shoulders than those homozygous for the A allele, after adjusting for birth weight. Significant associations (P < .05) between the parathyroid hormone-MspI marker and measures of body size were detected, as well as an effect on weaning weight (P = .03) as a maternal trait, whose magnitude (17.5 kg) equals the Brahman vs Angus and Hereford breed difference, as quantified in the diallel, and represents .8 of a phenotypic SD. No significant associations were found for three other marker-loci (prolactin-MspI, osteonectin-EcoRI, and keratin VI-MspI). Restriction fragment length polymorphisms have the potential to provide new insights and useful applications to animal breeding, but, as in this work, small sample sizes, extreme susceptibility to Type I errors, and different types of possible confounding obfuscate the conclusions that can be drawn from studies of limited scope and less than ideal planning.