Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.     

Direct and maternal genetic effects on preweaning characters of Brahman, Hereford and Brahman-Hereford crossbred cattle

Birth weight, preweaning gain and weaning weight (adjusted 180-d weight) data, collected at McGregor, Texas, were analyzed for genetic differences. Breedtypes represented in the data were Brahman, Hereford and various Brahman-Hereford crosses. Preweaning gain was calculated as adjusted 180-d weight less birth weight. All statistical models included effects of dam age, year, season and sex. Analyses were performed using a breedtype model and a regression model that redefined breedtype as direct additive, direct heterotic, maternal additive and maternal heterotic effects. Brahman dams produced calves with lightest birth weights. Brahman-sired calves were heaviest at birth compared with those by other sire breedtypes. The estimated Brahman direct additive effect on birth weight was 4.6 kg greater than Hereford. The Brahman maternal additive effect was 7.5 kg less than Hereford. Direct and maternal heterotic effects on birth weight were 2.2 and .6 kg, respectively. Calves from F1 dams had larger preweaning gains than those of the other breedtypes. The Brahman direct additive effect on preweaning gain was 17.7 kg less than Hereford and the Brahman maternal additive effect was 20 kg greater than Hereford. Direct and maternal heterotic effects on preweaning gain were 19.6 and 19.5 kg, respectively. Results of weaning weight analyses were similar to preweaning gain analyses. The largest effects on weaning weight were direct and maternal heterosis, which were 21.6 and 19.8 kg, respectively.     

Effects of an integrated control programme with ivermectin on growth, carcase composition and nematode infection of beef cattle in Argentina's western pampas

The effect of previous pasture management and ivermectin treatment on gastrointestinal parasitism, weight gain and carcase composition of steers was studied in the semiarid Pampeana region of Argentina from April 1986 to April 1987. Three groups, each of 15 weaned calves, were grazed on separate lucerne pastures. Group 1 control calves, which grazed paddocks previously grazed by nematode-infected weaners and yearlings with a high nematode egg output, were only medicated when heavy parasitism was recorded. Group 2 calves, which grazed paddocks previously infected by steers at least two and a half years old with low nematode egg output, were treated strategically with ivermectin. Group 3 calves, which grazed on 'clean' paddocks, were treated monthly with ivermectin. Group 1 calves showed heavy parasitism and parasitological parameters were higher than in groups 2 and 3. The liveweight gain responses of groups 2 and 3 were significantly greater than those of group 1 (P less than 0.001) during autumn, winter and early spring. At the end of the study when cattle reached market condition, the liveweight gains of groups 2 and 3 were 74.1 and 81.9 kg, respectively, greater than group 1. Carcase analyses showed significantly greater weight and killing-out percentages in groups 2 and 3 than in group 1. Reduced total bone, muscle and fat weights were observed in group 1.     

Effect of pre- and postweaning management system on the performance on Brahman crossbred feeder calves

During a 3-yr period (1986 through 1988), 117 calves (57 steers and 60 heifers) from the same genetic base and reared under four distinct preweaning management systems were weaned in the fall and transported from Uvalde, TX to El Reno, OK (800 km). Weaning weight and transportation shrink varied more from year to year than among preweaning treatments. Postweaning performance was not affected by preweaning treatment. After a 28- to 32-d receiving period the calves were blocked by sex and previous preweaning treatment, then randomly assigned within block to graze winter wheat forage (WHEAT) or dormant tall-grass native range (GRASS). The WHEAT group gained more (P less than .01) weight than the GRASS group during the winter (November to March), but when both groups were allowed to graze spring wheat pasture (March to June) the GRASS group gained more (P less than .01) weight than the WHEAT calves. During the subsequent finishing phase the GRASS calves were more (P less than .01) efficient than the WHEAT calves in converting DM to gain. Because cattle were slaughtered at the same degree of finish, no differences were noted in carcass characteristics among the pre- or postweaning treatments. Feeder calves exposed to a restrictive period of growth during the postweaning period gained weight more rapidly in a subsequent forage-based stockering system and were more efficient in a grain-based finishing system than nonrestricted calves.     

Genetic analyses of nematode egg counts in Hereford and crossbred Hereford cattle in the subtropics of New South Wales

A total of 438 calves was produced by 123 sires of Hereford, Simmental, Friesian and Brahman breeds when mated to Hereford cows. Faecal egg counts and larval differentiation of nematode species were undertaken on one or two occasions prior to weaning at 7 to 8 months. Significant breed of sire and sire within breed effects were observed, but heritabilities, repeatabilities and phenotypic correlations were generally low to moderate.     

Birth and weaning traits in crossbred cattle from Hereford, Angus, Brahman, Boran, Tuli, and Belgian Blue sires

The objective of this study was to characterize breeds representing diverse biological types for birth and weaning traits in crossbred cattle. Gestation length, calving difficulty, percentage of unassisted calving, percentage of perinatal survival, percentage of survival from birth to weaning, birth weight, BW at 200 d, and ADG were measured in 2,500 calves born and 2,395 calves weaned. Calves were obtained by mating Hereford, Angus, and MARC III (one-fourth Hereford, one-fourth Angus, one-fourth Pinzgauer, and one-fourth Red Poll) mature cows to Hereford or Angus (British breed), Brahman, Tuli, Boran, and Belgian Blue sires. Calves were born during the spring seasons of 1992, 1993, and 1994. Sire breed was significant for all traits (P < 0.002). Offspring from British breeds and the Belgian Blue breed had the shortest gestation length (285 d) when compared with progeny from other sire breeds (average of 291 d). Calving difficulty was greater in offspring from Brahman sires (1.24), whereas the offspring of Tuli sires had the least amount of calving difficulty (1.00). Offspring from all sire breeds had similar perinatal survival and survival from birth to weaning (average of 97.2 and 96.2%, respectively), with the exception of offspring from Brahman sires, which had less (92.8 and 90.4%, respectively). Progeny of Brahman sires were heaviest at birth (45.7 kg), followed by offspring from British breed, Boran, and Belgian Blue sires (average of 42.4 kg). The lightest offspring at birth were from Tuli sires (38.6 kg). Progeny derived from Brahman sires were the heaviest at 200 d (246 kg), and they grew faster (1.00 kg/d) than offspring from any other group. The progeny of British breeds and the Belgian Blue breed had an intermediate BW at 200 d (238 kg) and an intermediate ADG (average of 0.98 kg/d). The progeny of Boran and Tuli sires were the lightest at 200 d (227 kg) and had the least ADG (0.93 kg/d). Male calves had a longer gestation length, had a greater incidence of calving difficulty, had greater mortality to weaning, were heavier, and grew faster than female calves. Sire breed effects can be optimized by selection and use of appropriate crossbreeding systems.     

Pleiotropic effects in Hereford, Limousin, and Piedmontese F2 crossbred calves of genes controlling muscularity including the Piedmontese myostatin allele

Objectives were to determine 1) effects on traits measured from birth to slaughter in F2 cross calves from sire breeds that differ in potential for lean tissue growth but have similar mature BW and 2) the gene action of the mutant Piedmontese myostatin allele. Hereford (normal muscling, H), Limousin (moderate increase in muscling, L), and Piedmontese (muscular hypertrophy, P) sires (20 to 25 per breed) were bred at random to crossbred cows to produce F1 calves that were inter se-mated within sire breed to produce F2 calves that were grown out, finished, and slaughtered. Piedmontese-cross calves were genotyped for the G-A transition mutation at the myostatin locus characteristic of P (msP). Genotypes were classified on the basis of having zero (P0), one (P1), or two (P2) copies of msP (H, n = 227; L, n = 207; P0, n = 40; P1, n = 107; and P2, n = 37). Limousin-cross F2 calves had heavier birth (but dystocia was not affected) and weaning weights, gained faster, had more muscle, less fat, larger pelvic area, and more efficient feed conversion than Hereford-cross F2 calves. Normal-muscled Piedmontese-cross F2 calves (P0) were similar to Hereford-cross F2 calves except that they required less assistance at birth in heifer dams, had less fat, gained slower, were less efficient, and had larger pelvic area. Addition of msP alleles (P1 and P2) consistently increased muscle through hyperplasia, decreased fat, and increased adjusted efficiency, but many of those changes were not linear. Residual variances for breed were heterogeneous for most traits related to muscularity. This heterogeneity was caused by increased variances for L and P and(or) lower variances for H. Accounting for the msP alleles decreased the variance for P in most traits, but heterogeneity remained for most traits among the five genotypes because L remained high, H was low, and(or) P2 was low. We conclude that differences in muscularity affect most traits, and when differences in muscularity include the msP allele, there is an incremental, but not equal, change in most traits with the addition of each copy of the msP allele. Advantages of L could be captured through normal crossbreeding and selection schemes but with some caution because of potential problems from increased variability. Advantages of P could be best captured through more complex breeding and selection programs that would lessen potential negative impacts and through marketing systems that do not penalize for very low fat.     

Resistance of Santa Ines and crossbred ewes to naturally acquired gastrointestinal nematode infections

This trial was carried out in Piracicaba, São Paulo State, Brazil, to comparatively evaluate the degree of resistance to naturally acquired gastrointestinal nematode infections in sheep of the following genetic groups: purebred Santa Ines (SI), SI crossbred with Dorper (DO × SI), Ile de France (IF × SI), Suffolk (SU × SI), and Texel (TE × SI). Fifteen ewes from each group were raised indoors until 12 months of age. At this age, they were moved to pasture that was naturally contaminated by nematode infective larvae and were evaluated from December to May, 2007. Rainfall ranged from 267 mm in January to 37 mm in April. Maximum and minimum mean temperatures ranged from 32.5 °C to 19.0 °C in March and from 25.9 °C to 12.8 °C in May. There was an increase in the mean number of eggs per gram of feces (EPG) after animals were placed on pasture with significant difference between the SI (80 EPG) and IF × SI (347 EPG) groups in January; and the DO × SI (386 EPG) and TE × SI (258 EPG) groups in May. The highest mean fecal egg count (FEC), 2073 EPG, was recorded for the TE × SI group in February. All groups showed a progressive reduction in body weight throughout the experiment of 12.0% (TE × SI) to 15.9% (SU × SI). In general, the animals with the highest FEC presented the lowest packed cell volumes (PCV); the highest correlation coefficient between FEC × PCV occurred in the SU × SI sheep in January (r = −0.70; P < 0.01). Similarly, there was an inverse relationship between FEC and blood eosinophil values, with the highest correlation coefficient in the TE × SI sheep in February (r = −0.64; P < 0.05). Immunoglobulin G (IgG) levels against Haemonchus contortus antigens increased in all groups as a result of the exposure to parasites and remained relatively constant until the end of the study, with the exceptions of SU × SI and TE × SI, which showed a rise in IgG levels during the last sampling that coincided with a reduction in mean FEC. In conclusion, crossbreeding Santa Ines sheep with any of the breeds evaluated can result in a production increase and the maintenance of a satisfactory degree of infection resistance, especially against H. contortus and Trichostrongylus colubriformis, the major nematodes detected in this flock.     

Effects of Tuli,Brahman, Angus,and Polled Hereford Sires on Carcass Traits of Steer Offspring

Steer progeny (n = 122) of tropically adapted breeds [Tuli (TU) and Brahman (BR)] and temperate breeds [Angus (AN) and Hereford (HP)] was evaluated for carcass traits for 3 yr. Multiparous British (Bt) cows were bred to each sire breed. Following weaning in the fall, steers were provided bermudagrass hay and a supplement until rye was available, which they grazed until March. Steers were fed for 100 to 110 d beginning in March. Live weight (LWT); hot carcass weight (HCW); longissimus area (LEA); percentage kidney, pelvic, and heart fat (KPH); actual fat thickness (ACT); adjusted fat thickness (ADJ); marbling score(MARB); maturity score(MAT); quality grade (QG); yield grade (YG); dressing percentage(DP); and LEA per unit of LWT (LEACWT) were collected. Data were analyzed by Proc MIXED using a model that included year, sire breed, and year × sire breed. Sire breed was a significant source of variation for all traits except LEA. The effect of year was significant for all traits, and year × sire breed was significant for only LWT. Least square means for LWT and HCW ranked the breeds similarly; the AN-sired calves (576 kg, 333 kg) and BR-sired calves (574 kg, 334 kg) were heavier than the TU-sired calves (526 kg, 304 kg), and the HP-sired calves had intermediate LWT and HCW (562 kg, 320 kg). The actual and adjusted fat means were larger (P<0.02) for AN-sired calves, HP-sired cavles were intermediate, and the BR- and TU-sired steers were similar with less external fat. The TU-sired calves had the largest LEA relative to weight. The AN- and TU-sired groups had a similar percentage grading Choice (26 and 21%, respectively), and the percentage grading Choice for the other two sire breed groups was 12% for BR and 18% for HP. In conclusion, carcass merit of TU-sired calves provides an acceptable alternative to BR-sired calves for producers desiring a tropically adapted sire breed, but they will likely produce smaller slaughter BW than BR sires if managed similarly.     

Effect of postmortem treatments on the tenderness of meat from Hereford, Brahman and Brahman-cross beef cattle

The effect of postmortem aging (7, 14, 21 or 28 d), high-voltage electrical stimulation (stimulated or not stimulated) and blade tenderization (none or once; crossbreds only) on the sensory and cooking properties of meat from four beef breeds or breed-types (purebred Hereford, purebred Brahman, Hereford x Brahman and Brahman x Hereford) was determined. The meat from purebred Brahman cattle that was not electrically stimulated was less tender and more variable in tenderness than that from other breed-types but electrical stimulation reduced these differences in tenderness. The Brahman crossbred steers produced meat that was not different in tenderness or variability in tenderness from that of purebred Hereford steers, although all were only judged "slightly tender." Electrical stimulation reduced the length of postmortem aging needed to reach a given level of tenderness regardless of breed or breed-type. Meat from crossbred animals that was blade-tendernized was not different in tenderness from meat that was electrically stimulated. The results of this investigation indicate that purebred Brahman muscle was inherently less tender, but postmortem tenderization procedures produced meat that was similar tenderness to that of the other breed-types used in this study.     

Growth curves of crossbred cows sired by Hereford, Angus, Belgian Blue, Brahman, Boran, and Tuli bulls, and the fraction of mature body weight and height at puberty

The objective of this study was to evaluate the growth curves of females to determine if mature size and relative rates of maturation among breeds differed. Body weight and hip height data were fitted to the nonlinear function BW = f(age) = A - Be(k×age), where A is an estimate of mature BW and k determines the rate that BW or height moves from B to A. Cows represented progeny from 28 Hereford, 38 Angus, 25 Belgian Blue, 34 Brahman, 8 Boran, and 9 Tuli sires. Bulls from these breeds were mated by AI to Angus, Hereford, and MARC III composite (1/4 Angus, 1/4 Hereford, 1/4 Red Poll, and 1/4 Pinzgauer) cows to produce calves in 1992, 1993, and 1994. These matings resulted in 516 mature cows whose growth curves were subsequently evaluated. Hereford-sired cows tended to have heavier mature BW, as estimated by parameter A, than Angus- (P=0.09) and Brahman-sired cows (P=0.06), and were heavier than the other breeds (P < 0.001). Angus-sired cows were heavier than Boran- (P < 0.001) and Tuli-sired cows (P < 0.001), and tended to be heavier than Belgian Blue-sired cows (P=0.097). Angus-sired cows did not differ from Brahman-sired cows (P=0.94). Brahman-sired cows had a heavier mature BW than Boran- (P < 0.001), Tuli- (P < 0.001), and Belgian Blue-sired cows (P < 0.04). Angus-sired cows matured faster (k) than cows sired by Hereford (P=0.03), Brahman (P < 0.001), Boran (P=0.03), and Tuli (P < 0.001) sires, but did not differ from Belgian Blue-sired (P=0.13) cows. Brahman-sired cows took longer to mature than Boran- (P=0.03) or Belgian Blue-sired cows (P=0.003). Belgian Blue-sired cows were faster maturing than Tuli-sired cows (P=0.02). Brahman-sired cows had reached a greater proportion of their mature BW at puberty than had Hereford- (P < 0.001), Tuli- (P=0.003), and Belgian Blue-sired cows (P=0.001). Boran-sired cows tended to have reached a greater proportion of their mature BW at puberty than had Angus-sired cows (P=0.09), and had reached a greater proportion of their mature BW at puberty than had Hereford- (P < 0.001), Tuli- (P < 0.001), and Belgian Blue-sired cows (P < 0.001). Within species of cattle, the relative range in proportion of mature BW at puberty (Bos taurus 0.56 through 0.58, and Bos indicus 0.60) was highly conserved, suggesting that proportion of mature BW is a more robust predictor of age at puberty across breeds than is absolute weight or age.     

Effects of species and sex on plasma hormone and metabolite concentrations in crossbred Brahman cattle and crossbred water buffalo

Buffalo meat is tasty and indistinguishable from beef, and has been described as being lean and low in cholesterol in comparison with beef. However, little is known about the plasma hormone and metabolic profiles related to fat metabolism in buffalo, and how their levels are affected by species and sex. In this study levels of plasma hormones and metabolites were compared between species and sexes. Ten growing crossbred Brahman cattle and ten growing crossbred buffaloes (five males and five females in each), with an average age of 22 months were used. The animals were fed on an experimental diet composed of corn silage, brewer's spent grain and a concentrate mixture at a 50:30:20 ratio on a dry matter basis during a fattening period of 6 months. Blood samples were collected every month during the experiment, and were analysed for plasma leptin, insulin, glucose, triglyceride (TG) and total cholesterol (TC) concentrations. Plasma leptin, insulin and TC concentrations increased during fattening and were significantly (P < 0.05) higher in cattle than in buffaloes. These concentrations in cattle showed a big difference between sexes in comparison with buffaloes, and were higher in females than in males. The plasma glucose and TG concentrations did not differ (P > 0.05) between cattle and buffaloes.

The crude fat content of longissimus muscle was significantly higher in cattle than in buffalo. Differences in body fat deposition seem to have an influence on plasma leptin, insulin and TC concentrations differently between cattle and buffaloes.     

Effect of naturally occurring nematode infections on growth performance of first-season grazing calves

Liveweight of calves on 89 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection during the grazing season. There were significant between-herd variations in antibody titres against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus as well as in pepsinogen values. All but six herds (93.1%) had gastrointestinal nematode infections, as measured by faecal egg counts in September. Faecal samples of 17 herds (19.3%) contained lungworm larvae in September. Liveweight of calves per herd deviated from -68.1 kg to +84.1 kg from the age-adjusted population mean after their first grazing season. Growth performance up to the time of liveweight measurements was significantly correlated negatively with several serological and parasitological parameters. Data could be fitted by means of both linear and segmented curvilinear regression. Antibody titre against Cooperia spp. and gastrointestinal nematode egg output measured in September accounted for 3.1% (P less than 0.10) and 6.7% (P less than 0.05), respectively, of the variation in growth performance among herds. Certain infection parameters, when combined, accounted for 9.2% of this variation; these were antibody titre against Cooperia spp. and larval counts for both gastrointestinal nematodes and lungworm. Adding certain management factors to these infection parameters resulted in a model explaining 27.6% of the observed variation in growth performance among herds. These factors were supplementary feeding, lungworm vaccination, anthelmintic treatment at housing, date of housing and herd age.     

Maternal performance of Hereford, Brangus, and reciprocal crossbred cows under semidesert conditions.

Maternal performance of 134 Hereford (H), Brangus (B), and reciprocal crossbred (H x B and B x H) cows from 2 to 7 yr of age was evaluated under semidesert conditions in this study. Calves produced by 2- and 3-yr-old cows were sired by Brangus and Hereford bulls. Calves produced by 4- to 7-yr-old cows were sired by Charolais bulls. Breed of sire and breed of dam of cow affected kilograms of weaning weight, 205-d weight, weaning weight as a percentage of cow weight, and 205-d weight as a percentage of cow weight produced annually. Brangus (either as sire or dam of cow) was superior to Hereford in all cases. Observed maternal heterosis on 2- to 3-yr-old cows was 23.0, 20.1, 30.0, 29.1, 23.9, and 23.0% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Observed maternal heterosis from mature cows was 19.8, 12.8, 21.0, 18.7, 17.4, and 15.4% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Results indicate large heterotic effects on annual cow productivity and an adaptive advantage for cows with Brangus sires and(or) dams under semidesert conditions.     

Effect of restricted feeding on metabolic adaptations of Kamphaengsaen and crossbred Brahman heifers

Metabolic adaptation during feed deprivation was determined in five Kamphaengsaen (KPS) and six crossbred Brahman (Crossbred Bra) heifers. All heifers were fed at the rate of 85% of the metabolizable energy requirement for maintenance. At the end of 20 days of restricted feeding, the Crossbred Bra heifers lost more bodyweight than the KPS heifers (12.0 vs. 7.2 kg) (P < 0.05). In both groups of heifers there was a similar depletion of back‐fat thickness, however, the loin eye area of the Crossbred Bra heifers decreased more than KPS heifers (8.43 vs. 0.92%; P < 0.05). Feed restriction elevated the rate of lipolysis in adipose tissue, resulting in increased nonesterified fatty acids concentrations in plasma. The Crossbred Bra heifers had a greater serum high density lipoprotein triacylglycerol concentration than the KPS heifers (17.02 vs. 9.53 mg/dL; P < 0.05). This would suggest that the hepatic tissues in the Crossbred Bra heifers exported more triacylglycerols as very low density lipoprotein than in the KPS heifers. During the feed restriction period, the plasma β‐hydroxybutyrate concentration for the heifers was elevated; however, Crossbred Bra heifers shown less plasma β‐hydroxybutyrate concentration than KPS heifers (242 vs. 326 µmol/L; P < 0.05). This may be due to the difference in very low density lipoprotein secretion between the two groups of heifers. There were significant differences in plasma urea‐nitrogen and plasma glucose concentrations (P < 0.05), with the KPS heifers showing less extensive plasma urea‐nitrogen concentration and hypoglycemia, whereas the Crossbred Bra heifers had more extensive plasma urea‐nitrogen concentration and euglycemia. These two metabolites were suggestive of a ketogenic effect on muscle protein catabolism. In conclusion, it was found that the underfed KPS heifers utilized ketone bodies as their energy source, thus limiting body protein degradation, whereas the Crossbred Bra adapted to feed deprivation by exhibiting an auto‐regulation mechanism for ketogenesis and broke down body protein extensively to satisfy their demand for glucose.     

Effect of location and season on body and testicular growth in Brahman and Hereford bulls

To determine the effects of location and season on growth of bulls, Hereford bulls from Montana (MH; n = 15) and Nebraska (NH; n = 15) and Brahman bulls from Texas and Louisiana (BB; n = 18) were moved to three locations: Montana (MT), Nebraska (NE) or Texas (TX). Each location received 5 NH, 5 MH and 6 BB. Control bulls (not relocated) were maintained at each location. All bulls were pubertal at the time of relocation in May 1984. At 28-d intervals, body weight, hip height, testis length and scrotal circumference were recorded for each bull for 22 mo after relocation. Paired testes volume (PTV) was calculated. Among Hereford bulls, body weights were similar (P greater than .10) in all control and relocated bulls by the end of the study, except that MH bulls moved to TX had lower body weights (P less than .01). Brahman bulls moved to northern locations had dramatically reduced body weights, compared to control Brahmans kept in TX; body weight of Brahman bulls in MT remained lower (P less than .01) at the end of the study. Brahman bulls in NE and MT had smaller scrotal circumference and PTV (P less than .01) than did control Brahmans in TX during the 1st yr after relocation. Relocated BB exhibited marked seasonal fluctuations in testis size, with increases during the summer and decreases during the winter (P less than .01); seasonal changes were not apparent in control Brahmans in TX. These results indicate that moving Brahman bulls to northern environments reduced body weight gain and caused dramatic seasonal changes in testis size; these effects were more pronounced in Brahman bulls moved to the most northern location.     

Effect of nematode infections and management practices on growth performance of calves on commercial dairy farms

Liveweight of calves on 86 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection estimated in October and December. There were significant between-herd variations in all the serological infection parameters measured. On average 20.5 larvae per gram faeces (geometric mean) were found in October. Faecal samples of 20.5% of the herds contained lungworm larvae. Liveweight of calves deviated per herd from -59.8 kg to +52.2 kg from an age-adjusted population mean after their first grazing season. Growth performance was significantly related negatively to several serological and parasitological parameters. Data were fitted by means of both linear and segmented curvilinear regression. By combining infection parameters 19% of the variation in growth performance among herds could be explained. Infection parameters involved were antibody titre against Cooperia spp., egg output and lungworm larval count. It was found that antibody titres were significantly correlated positively to herd age, while pepsinogen values and egg output were negatively correlated to age. Combining supplementary feeding and anthelmintic treatment during the grazing season with the infection parameters into one model explained approximately 30% of the observed variation in growth performance among herds. It was shown that these findings were consistent with those of a similar study conducted on the same farms a year earlier, although there were clear differences between the years. Finally, significant positive relations were found between the levels of exposure to nematode parasites within farms between two consecutive years.