Productivity of pure- and crossbred cattle in a subtropical environment

The influence of different breeds of sire and dam types on cow productivity in an arid, subtropical environment was studied. Cows with calves sired by Simmentaler, Hereford and Bonsmara bulls were more (P<0.05) productive than those with calves sired by Afrikaner bulls. Simmentaler sires were superior (P<0.05) to Bonsmara sires. Crossbred cows of predominant (>50%)Bos taurus breeding were generally superior to crossbreds of predominantB. indicus breeding and purebreds. Crossbreeding systems to utilize breed effects to optimise cow productivity within environmental constraints are discussed.     

Ultrasonographic fetal parameters and neonatal survival in somatic cell nuclear transfer–derived beef calves

The objectives of this study were to identify prognostic indicators of calf survival in SCNT-derived beef calves. Ultrasonographic parameters of fetal well-being and development, maternal clinical parameters, and neonatal parameters were evaluated as predictors of calf survival in cows carrying SCNT-derived beef fetuses (n = 38). Calf survival was 61.5% (88.2% female and 40.9% male calves; P = 0.0026). Cow respiratory rate and cow temperature were significantly greater in the nonsurviving (NS) group 1 week prepartum. In surviving (S) calves, fetal heart rate (FHR) decreased during the last 2 weeks of gestation (P < 0.01). However, this final deceleration was not observed in NS calves, resulting in higher FHRs in this group (P < 0.0001). Fetal movement and fluid scores did not differ with calf classification. Mean amniotic fluid depth was smaller in S (5.5 ± 0.7 cm) than NS (8.7 ± 1.4 cm) calves (P = 0.0398). However, mean allantoic fluid depth did not differ (P = 0.6120). There was a significant association between the body weight of calf and the diameter of the fetal aorta (P = 0.0115; r² = 0.3762). Surviving calves were lighter at birth (P = 0.0028) and were born later (P = 0.007) than NS calves. Calves born vaginally had a smaller fetal aorta (2.1 ± 0.1 cm vaginal and 2.4 ± 0.1 cm Cesarean) (P = 0.0487) and a lighter birth weight (41.4 ± 4.2 kg vaginal and 60.4 ± 2.1 kg Cesarean) (P = 0.0001) than calves born by Cesarean. Also, calves that underwent spontaneous labor (52.2% S and 0% NS; P = 0.0029) had a lighter birth weight (44.9 ± 3.8 kg) than calves that did not initiate labor (61.6 ± 2.2 kg) (P = 0.0004). Frequent ultrasonographic fetal monitoring allowed identification of differences between S and NS calves. Calves without a final decrease in FHR or with a large aortic diameter were more likely to require a Cesarean because of failure to initiate labor or fetomaternal disproportion. Parameters of fetal well-being and development during the last 3 weeks of gestation were first described in SCNT-derived beef calves.     

Resistance of indigenous African cattle to the tickAmblyomma hebraeum

Field collections ofAmblyomma hebraeum Koch adults from six breeds of cattle were conducted on two farms in the Northern Transvaal. The density ofA. hebraeum adults was highest on Simmentaler cows, followed by Santa gertrudis, Africaner, Bonsmara, Brahman and Nguni. Indigenous breeds, namely Nguni, Bonsmara and Africaner, have the highest level of resistance toA. hebraeum. The relationship between tick abundance and the high level of resistance found in the indigenous breeds is discussed.     

Effects of pre-weaning concentrate feeding on calf performance, carcass and meat quality of autumn-born bull calves weaned at 90 or 150 days of age

A study was conducted to evaluate the effect of pre-weaning concentrate feeding in early-weaned (EW, day 90) or traditionally weaned (TW, day 150) autumn-born beef calves on growth, feed intake and feed efficiency, and carcass and meat quality. Twenty-eight male calves were either EW or TW, and offered a starter concentrate (S) or no additional feed (NS) during the pre-weaning period. Therefore, four management strategies were tested: EWS, EWNS, TWS and TWNS. Growth patterns were affected by management strategy. From day 90 to 150, TWNS calves presented a substantially lower average daily gain (ADG) than their counterparts, which had similar performance. During the finishing phase (from day 150 to slaughter at 450 kg live weight), EWS calves had the lowest ADG. Daily feed intake or efficiency in the finishing phase was unaffected by previous management. Serum IGF-I concentrations at day 90 and slaughter did not differ with management strategy, but early weaning and pre-weaning concentrate feeding increased IGF-I concentrations at day 150. Circulating leptin concentrations were unaffected by age at weaning and pre-weaning concentrate feeding, except for leptin concentrations at slaughter, which were higher in S calves than in NS calves. Total concentrate intake from birth to slaughter and the concomitant feed costs were higher for EWS and EWNS calves than for TWNS and TWS ones. However, cow feed costs were lower for cows whose calves had been early weaned. Concerning carcass quality, early weaning improved dressing percentage and increased fatness score, and particularly TWNS calves presented a poorer conformation. Meat quality was not affected by management strategy. Considering the economic performance, TWS, EWNS and EWS strategies yielded a similar economic margin, whereas TWNS would be the least advisable strategy when calves are fattened in the farm until slaughter.     

Animal performance and stress at weaning when dairy cows suckle their calves for short versus long daily durations

Calves in most dairy farms are separated from their dams either immediately or within a few hours after birth, prompting increasing concern of the society for reasons of animal welfare. The aim of this study was to identify systems to maintain cow-calf contact (CCC) that balance the benefits for calf growth and health against the negative impacts on sellable milk and stress at weaning. We tested reuniting cows and calves for 20 min before (Before-group) or 2.5 h after (After-group) morning milking (in Trial 1) or for a 9 h period between the morning and evening milkings (Half-day-group, in Trial 2). In Control-groups, calves were separated from their dam at birth and fed with artificial nipple with tank milk provided daily at 13% (Trial 1) and 14% (Trial 2) of their BW. In both trials, each practice was applied on a group of 14 dam–calf pairs (7 Holstein [Ho] and 7 Montbéliarde [Mo]). All calves were weaned at a BW of at least 100 kg. In Trial 1, the After-group was prematurely stopped when the calves were eight weeks of age as calf growth became limited (340 g/d) due to low milk intakes (2.97 kg/d). During the first eight weeks of lactation, milk yield at the parlour was 29%, 51% and 42% lower in After-, Before- and Half-day-cows respectively compared to Controls. From week 14 to 16 when all calves were separated from their dam, Before-cows still produced 25% less milk than Control-cows while Half-day-cows reached the milk yield of Control-cows within a week. There were no significant differences in milk somatic cell count and in frequency of health disorders (cows and calves) between suckling and Control-groups. Compared to Control-calves, calf growth until weaning was higher in the suckling calves in Trial 1 (861 vs 699 g/d) and similar in Trial 2 (943 vs 929 g/d). At weaning, Before- and Half-day-calves started to vocalise earlier and continued to vocalise longer than Controls. In conclusion, the best compromise between cow milk yield and calf growth is a long period of CCC (9 h) between the morning and evening milkings. Still abrupt weaning stresses both cows and calves even if CCC has been restricted before separation.     

Increasing preweaning milk replacer supply affects postweaning energy metabolism of Holstein male calves

Male Holstein calves commonly receive minimal quantities of milk replacer (MR) to speed up weaning and reduce costs. Studies with Holstein female calves show that early life feed restriction affects energy metabolism later in life. Aiming to test this hypothesis, 120 Holstein bull calves (48.4 ± 2.2 kg of BW and 20 ± 3.2 d of age) housed in 24 pens were blocked and randomized to two treatments: A low calf MR allowance (LP) (two daily doses of 2 l each, 582 g/d of DM), or a high MR allowance (HP) (two daily meals of 4 l each, 1 164 g/d of DM). Calves were weaned at day 49 of the study and slaughtered at 32.8 ± 0.5 weeks of age. Throughout the study, animals had ad libitum access to a common compound feed, straw, and water. Twenty-four animals were randomly selected for an intravenous glucose tolerance test (IVGTT). The IVGTT was performed at week 6 and 12 of the study and consisted of an intravenous glucose infusion and sequential blood sampling up to 90 min after glucose infusions. Calves were heavier for HP until week 12, after which the difference disappeared. By design, the MR intake was higher in the HP group resulting in a higher energy intake and a higher average daily gain in the preweaning phase. Blood glucose curves were not different at week 6, but at week 12, 5 min after the infusion, glucose was higher in HP calves. Insulin curves were not different at week 6. Nevertheless, in week 12, a higher insulin concentration was observed for HP 5, 10, 15, 20, 30, 35, and 45 min’ postinfusion, indicating a higher requirement of insulin to control glycemia. Differences between HP and LP calves were also observed for the quantitative insulin sensitivity check index, maximum insulin concentration, and insulin delta at week 12. Blood glucose reached maximum concentration within 5–10 min of the IVGTT test, and the concentration was, on average, 8.58 and 10.80 mmol/l at weeks 6 and 12, respectively. Insulin reached maximum concentration within 10–15 min of the IVGTT, and concentrations were, on average, 33.32 and 32.61 μUI/ml at weeks 6 and 12, respectively. Doubling MR supply improved animal growth up to weaning, but these differences disappeared by the end of the feeding period. Despite similar responses to glucose infusions preweaning, higher milk supply seemed to decrease insulin sensitivity after weaning.     

Performance of ad libitum fed dairy calves weaned using fixed and individual methods

The increasing availability of automated milk dispensers on dairy farms facilitates ad libitum milk supply but weaning calves from high milk allowances is challenging. This study evaluated effects of gradual weaning methods on starter intake, growth, selected blood parameters and weaning distress in ad libitum fed dairy calves during weaning and early post-weaning periods. Thirty-six male Holstein (n = 30) or crossbred (n = 6) calves were individually housed from days 2 to 14 of age and had ad libitum access to milk replacer (MR) from teat buckets. From days 15 to 84 of age, calves were grouped and had ad libitum access to MR, starter, straw and water from automated feeders. At day 35, calves were blocked (age and breed), and randomly assigned to a weaning method: (1) linear fixed (LIN), MR supply was stepped down to 6 l/day on day 36, and linearly reduced between days 36 to 63 from 6 to 2 l/day. (2) Step-down (STEP), MR supply was stepped down to 6 l/day from days 36 to 48, 4 l/day from days 49 to 56 and 2 l/day from days 57 to 63. (3) Dynamic (DYN), at day 36, MR supply was reduced for each individual calf to 75% of the average voluntary consumption between day 29 and 35, then maintained for 9 days, reduced to 50% for 10 days, and to 25% for 9 days. The DYN calves received more MR during weaning than LIN calves, whereas STEP calves had intermediate MR intake. Starter intake was not affected by weaning method. The DYN calves (1.33±0.08 kg/day) grew faster and were heavier than STEP calves (1.10±0.08 kg/day) during post-weaning period, whereas no difference was observed between LIN calves (1.23±0.08 kg/day) and others. At days 70 and 84, concentrations of β-hydroxybutyric acid were higher in LIN calves compared to STEP and DYN calves. Hair cortisol concentrations were not affected by weaning method. During the gradual weaning process CP intake seemed to recovered earlier than metabolizable energy (ME) intake in all treatments, suggesting that ME rather than CP could be the first limiting factor for growth during weaning. These results highlight the post-weaning benefits of DYN and LIN weaning methods when compared with more abrupt step-down strategies.     

早期断奶对犊牛生产性能和母牦牛繁殖性能的影响

本试验旨在研究早期断奶对犊牛生产性能和母牦牛繁殖性能的影响。试验组采取"全哺乳+早期诱饲+补饲+放牧+早期断奶"的模式进行饲养,对照组采取传统放牧。实验表明:试验组犊牛5月龄实现早期断奶,体重极显著高于对照组(p<0.01)((53.13±12.34) kg VS (23.44±9.38) kg);试验组犊牛7月龄时体重达71.42 kg,比对照组提高了1.36倍;血液检测分析:与对照组相比,试验组显著提高了牛表皮生长因子(p<0.05);12月龄时体重极显著高于对照组(p<0.01)((87.25±23.43) kg VS (39.51±17.28) kg);当年生犊牦牛实施早期断奶,母牦牛进入下一个繁殖周期,其"一年一胎"比例达68.6%。因此,早期断奶尚未影响犊牦牛生长发育,同时有利于母牦牛年产犊的提高。     

Effect of pre-weaning feeding regimens on post-weaning growth performance of Sahiwal calves

The objective of the study was to assess the post-weaning growth response of Sahiwal calves reared on four different pre-weaning dietary regimens. The four diets were: (a) whole cow's milk, starter ration (SR; CP = 20%, total digestible nutrients (TDN) = 72%) and Berseem hay (H; Egyptian clover; CP = 21%, TDN = 63%); (b) whole cow's milk + H; (c) milk replacer (MR; reconstituted to supplier specification; Sprayfo®) + SR + H; and (d) MR + H. The protein and fat percentages of reconstituted MR were 2.22 and 1.84, respectively. Milk or MR were fed at the rate of 10% of the calves’ body weight (BW) until 56 days of age, and then withdrawn gradually until weaned completely by 84 days of age. The average initial BW of calves in groups A, B, C and D were 56.3 ± 1.0, 47.5 ± 1.0, 40.4 ± 1.0 and 30.3 ± 1.0 kg, respectively. Initially, there were 12 calves in each group with six of each sex; however, one male calf died from each of groups B and C and were not replaced. During the post-weaning period, 13 to 24 weeks, the calves were fed a single total mixed ration ad libitum based on maize, canola meal, wheat straw and molasses containing 16% CP and 70% TDN. Daily feed intake and weekly BW gains were recorded. The data were analyzed by MIXED model analysis procedures using the statistical program SAS. The intake of calves as percent of their BW, feed conversion ratio and cost per kg of BW gain were not different (P > 0.05) across treatments. The daily gain at 24 weeks of age for the pre-weaning treatments A, B, C and D were 746 ± 33, 660 ± 33, 654 ± 33 and 527 ± 33 g/day and the final liveweights of calves were 119 ± 4.2, 102 ± 4.2, 95 ± 4.2 and 75 ± 4.2 kg, respectively. Gains were influenced significantly (P < 0.05) by pre-weaning treatments. The calves fed MR and H only during the pre-weaning period were unable to catch up post weaning with calves on other dietary treatments. The calves fed whole milk from birth at the rate of 10% of liveweight together with concentrates had higher weaning weight and superior growth rate post weaning as well. Thus, pre-weaning feeding was important for higher weaning weights and superior growth rates post weaning.     

Influence of 48 hour calf separation on milk production and calf growth in range cows

Hereford cows and their calves were either left together or separated for a 48-hr period between 50 and 80 days postpartum. Milk production and calf weights were determined 1 and 2 weeks prior to and 1 and 3 weeks after calf separation. Daily milk production of separated cows (5.6+/-.1 kg) was not different from that of control cows (5.3+/-.1 kg) at any sampling period. Similarly, calf growth was not affected (P > .10) by separation; both groups of calves gained .64 kg/day. Average 205-day adjusted weaning weights were also similar, for the control (173.5+/-4.6 kg) and separated calves (181.8+/-4.6 kg). These results indicate that 48-hr calf separation could be used in a treatment regime to decrease the postpartum anestrous interval in range cattle without detrimental effects on milk production, calf growth or 205-day adjusted weaning weight.     

Short- and long-term effects of temporary early cow–calf separation or restricted suckling on well-being and performance in zebu cattle

Information on weaning techniques in the tropics is scarce, particularly regarding the long-term effect of temporary early cow–calf separation or restricted suckling. Therefore, we studied the effects of these two handling practices on well-being and performance at 150 days postpartum in fifteen zebu cow–calf pairs randomly assigned to three treatments. Continuous suckling (CS) where calves remained with their dams from birth to weaning; restricted suckling (RS) calves were allowed to suckle 30 min/day from Day 34 until weaning at Day 150 and kept separated the rest of the time; temporary separation (TS) calves were separated for 72 h from their dams from Day 33 to 36 but remained with their dams the rest of the time. Blood samples and behavioral data were collected on Days 32–36 (1st period) and 149–153 (2nd period). In the 1st period, a greater percentage of RS and TS calves were observed close to the fence line (< 10 m) that separated them from their dams (P < 0.0001) and vocalized more than CS calves (P < 0.0001), while in the 2nd period, RS calves had the highest cortisol concentration and vocalization rate (P < 0.05). Similarly, during the 1st period, a greater percentage of RS and TS cows were observed close to the fence line than CS cows (P < 0.0001), with TS cows vocalizing the most (P = 0.001). In the 2nd period, RS cows had greater cortisol concentration than TS (P = 0.037) and CS cows (P = 0.003). More TS and CS cows than RS were observed close to the fence line (P = 0.03 and P = 0.05). On Day 150, TS calves and cows vocalized more than RS and CS animals (P < 0.0001). Before calf–cow separation, 27 out of 45 cows were cycling (CS = 10; RS = 6; TS = 11). After separation, 12 of the remaining 18 cows resumed ovarian activity (CS = 3; RS = 5; TS = 4), and all cows were cycling after estrous synchronization treatment. The pregnancy rate was similar between CS, RS, and TS (60, 53, and 60% respectively). In conclusion, temporary separation increased calf distress response to definitive weaning even four months later, while restricted suckling seemed to reduce it.     

Minimizing cows’ stress when calves were early weaned using the two-step method with nose flaps

Early weaning may be used in beef cattle production to improve reproduction rates in range conditions. However, weaning causes a stress response in cows, which may be especially strong in early weaning management, as the bond between the cow and the calf is still strong. We hypothesized that weaning calves in two steps, with the aid of anti-sucking devices (nose flaps) would reduce the behavioural stress response in the cows separated from their calves 2 months after parturition. We compared the behaviour frequency and weight change in cows that were weaned abruptly, by separation of the calf on day 0 of the study, or in two steps, consisting of the use of anti-sucking nose flaps for 5 days before permanent separation; a third group was not weaned to serve as control. Thirty-six crossbred multiparous Aberdeen Angus×Hereford cows and their calves (n=12/treatment) were managed in three paddocks with similar pasture availability, with four dyads from each treatment per paddock. Cows’ behaviour was observed by direct visual instantaneous sampling, at 10 min intervals from days −3 to 11. Weaning the calves in two steps clearly attenuated the behavioural stress response observed in abruptly weaned cows, which included reductions in grazing and lying, and increases in pacing, walking and vocalizing. Our results corroborate those previously shown for cows nursing older calves, and indicate that step weaning can reduce the behavioural stress response of cows at weaning, even when the calf is weaned shortly after birth, when the bond between the cow and calf is still very strong.     

Effect of rumen-protected methionine supplementation to beef cows during the periconception period on performance of cows,calves, and subsequent offspring

Maternal nutrition affects the development of the fetus and postnatal performance of the calf. Methionine may play a critical role in developmental programming and is likely deficient in beef cows fed low-quality forage. The objective of this study was to determine the effect of metabolizable methionine supply to lactating beef cows during the periconception period on performance of cows, calves, and subsequent offspring. This project involved two consecutive production cycles commencing at calving in which dietary treatments were fed to cows during the periconception period along with measurements on cows and initial calves in Production Cycle 1, and measurements on subsequent calves in Production Cycle 2. Brangus-Angus crossbred lactating beef cows (N = 108; age = 6.4 (2.8) year) were stratified by previous calving date and assigned to one of three supplements: (1) control, molasses plus urea at 2.72 kg/day as fed, (2) fishmeal, 2.27 kg/day molasses plus urea plus 0.33 kg/day as fed of fishmeal, and (3) methionine, 2.72 kg/day of molasses plus urea plus 9.5 g/day of 2-hydroxy-4-(methylthio)-butanoic acid. Cows were fed supplements and low-quality limpograss (Hemarthria altissima) hay while grazing dormant bahiagrass (Paspalum notatum Flüggé) pastures during the 115-day periconception period from December 2014 to April 2015 in Production Cycle 1 only. Body weight change and milk yield of cows were measured during the periconception period in Production Cycle 1. Body weight of calves was measured at birth and weaning in both production cycles. Following weaning in Production Cycle 2, eight subsequent steer calves per treatment were individually housed for a 42-day metabolism experiment. Treatment did not affect (P > 0.10) BW change of cows, but cows fed methionine tended (P = 0.09) to produce more energy-corrected milk than control and fishmeal. Treatment did not affect (P > 0.10) 205-day adjusted weaning weight of calves in either production cycle. During the metabolism experiment, subsequent calves from dams fed fishmeal and methionine gained faster (P < 0.05) and had greater (P < 0.05) gain:feed than control calves. Methionine calves tended (P = 0.06) to have greater apparent total tract NDF and ADF digestibility and lesser (P < 0.05) blood glucose concentration than control and fishmeal calves. These data indicate that maternal methionine supply during the periconception period plays an important role in programming future performance of the offspring.     

Weaning distress in dairy calves: Effects of alternative weaning procedures

The aims of this study were to describe the behavioural responses to weaning from milk in dairy calves, and to compare responses when calves were either weaned abruptly (removal of the milk-feeding system; n = 8 calves) or by substituting warm water for milk in the milk-feeding apparatus for the first 2 days after weaning (n = 8 calves). Calves provided water through the milk-feeding system after weaning seemed to substitute one liquid for the other; calves consumed approximately the same quantity of warm water after weaning (8 kg/day) as they had consumed milk before weaning (9 kg/day). All calves vocalized at weaning, but abruptly weaned calves vocalized at more than three times the rate of calves provided water through the milk-feeding system. On the third day after weaning, when neither treatment group had access to the milk-feeding system, the call rate was similar in the two treatment groups. The abruptly weaned calves were also more active at weaning, as indicated by an increased number of standing bouts compared to calves with continued access to the milk-feeding apparatus. The reduced response to weaning by the calves with continued access to the feeding routine may be due to the gut fill associated with the water intake or to other rewarding properties of the system (e.g. allowing calves to suck on a teat). In conclusion, dairy calves show a strong behavioural response to weaning, but providing calves continued access to the milk-feeding apparatus for 2 days after weaning reduces this response.     

Neonatal Milestones,Behavior and Growth Rate of Sumatran Rhinoceros (Dicerorhinus sumatrensis) Calves Born and Bred in Captivity

The birth of Sumatran rhino calves at the Cincinnati Zoo and Botanical Garden offered a unique opportunity to study early development and cow–calf behavior in this elusive, critically endangered species. Study goals were to: (1) record developmental milestones of newborn calves; (2) characterize cow and calf behavior during the first year following birth; (3) compare trends in the behavioral development of a male vs. female calf; and (4) record weight gain and footprint size throughout the first year. In addition to recording eight neonatal milestones, more than 450 hr of behavioral data were collected on each of the two calves (one male and one female) and their dam during the first 12 months of life. Neonatal milestones were achieved within 24 hr of birth with the exception of first defecation, which occurred at 16–18 days. Although nursing bouts decreased slightly in the second half of the year (from once every 90 min to once every 2 hr), they continued to occur frequently throughout the day and night. Therefore, calves grew rapidly from approximately 33 kg at birth to 400 kg at 12 months. Average daily weight gain for the first week was approximately 2.0 kg, whereas average daily weight gain for the remaining 12 months was slight (<1 kg) and did not differ between calves. Eating and resting occupied 70–80% of the Sumatran rhino cow and calves' time and no gender biases in either maternal investment or developmental parameters were noted. Finally, footprint measurements proved valuable for estimating calf age. Zoo Biol 31:546‐560, 2012. © 2011 Wiley Periodicals, Inc.     

Evaluation of productivity of sexually precocious Nelore heifers

The objectives of the present study were to investigate the influence of yearling weight on the occurrence of early pregnancy and to determine differences between precocious and non-precocious heifers in terms of pre- and postnatal calf mortality, calf weight and height, mature cow weight, and stayability of the cow in the herd. Data from 26 977 females of a Nelore herd that participated in the breeding season between 1986 and 2004 were analyzed. The influence of yearling weight on sexual precocity and differences between precocious and non-precocious heifers in pre- and postnatal calf mortality and stayability were analyzed using the GENMOD procedure of the SAS program. Differences in the growth traits between precocious and non-precocious animals were estimated by contrast analysis. Three groups were analyzed for postnatal mortality: first calving of the heifers, calves born from the third calving and all offspring of the cow. In order to have a standardized calving to conception period for all females (precocious and non-precocious), calves born from the second calving were not included in the analysis. This was necessary because the first calving to conception period (days open) of precocious heifers was longer than for non-precocious due to farm reproductive management. No differences in postnatal mortality rates, from the third calving, were observed between the two groups of heifers studied. Analysis of all offspring of the dams showed a 9% higher probability of death of calves born to precocious heifers compared with calves born to non-precocious heifers. With respect to stayability, precocious heifers presented 33% greater odds to remain in the herd until 5 and 6 years of age and 28% greater odds to remain in the herd until 7 years when compared with non-precocious heifers. Precocious heifers weaned calves (205 days) significantly heavier than non-precocious ones, 1.410 and 0.797 kg considering the weaning weights of all offspring and of the third calving, respectively. With respect to sexual precocity, the results suggest that the probability of heifers to become pregnant at 16 months of age increases with increasing weight. However, heifers weighing more than 240 kg present practically the same pregnancy probability. Nevertheless, exposure of heifers during the early breeding season is recommended for beef cattle herds raised in tropical regions in view of the numerous benefits demonstrated here.     

Effect of daily concentrate intake at weaning on performance of belgian blue double-muscled rearing calves

Abstract

Weaning at a different daily concentrate intake was investigated during a 140-d experimental period, using 54 male and 68 female newborn Belgian Blue double-muscled animals. They were divided into three comparable groups and received milk at 10% of their birth weight up to weaning. Concentrate was levelled off at a maximum daily intake of 3 kg, while grass hay was freely available. Weaning occurred at a daily concentrate intake level (CL) of 0.5, 0.75 and 1.0 kg, respectively. Weaning at an increased CL prolonged the milk-feeding period by 13.1 and 14.6 days, and resulted in a higher pre- and post-weaning growth rate (p < 0.05). Daily gain during the entire experimental period averaged 0.84, 0.85 and 0.88 kg for the respective groups (p = 0.065). Daily concentrate intake was not different among groups, with only a small effect of CL on intake around weaning. Early weaning resulted in a significant reduction of hay intake (p = 0.032). Total daily net energy intake increased slightly with a higher CL at weaning, so that energy conversion was slightly improved, amounting to 17.7, 17.6 and 17.4 MJ/kg gain, respectively. Energy balance during the first week after weaning was negative for CL 0.5 kg (?22%), while it was close to 0 for CL 0.75 kg (?2%) or positive for CL 1.0 kg. Most effects of CL at weaning were similar for males and females, but male calves tended to have a higher intake and a faster growth rate than females. It can be concluded that weaning should be delayed until Belgian Blue double-muscled calves consume at least 0.75 kg per day or more for reasons of welfare, although performance was hardly improved by weaning at a daily concentrate intake of more than 0.5 kg per day.     

Effects of castration and weaning conducted concurrently or consecutively on behaviour,blood traits and performance in beef calves

The objectives of this study were to evaluate the effects of Burdizzo castration and abrupt weaning on the behaviour, blood traits and performance of beef calves when weaning was conducted concurrently or consecutively to castration. In total, 64 male beef calves aged between 6 and 7 months were assigned to a 2×2 factorial design with the following treatment groups (n=16 animals per treatment): (1) castrated and concurrently weaned in week 0 (CAS-WEA); (2) castrated in week 0 and weaned in week 4 (CAS-CON); (3) bulls weaned in week 0 (BUL-WEA); and (4) bulls weaned in week 4 (BUL-CON). The behaviour of the calves was observed for 3 days following weaning. Blood was collected weekly from weeks 0 to 5 and analysed for the acute-phase protein haptoglobin, and neutrophil and lymphocyte percentages. BW was recorded weekly from weeks 0 to 7. Animals were slaughtered at 17 months and weight, dressing percentage and carcass classifications were recorded. On day 1 after weaning, the number of vocalizations (calls/10 min) was higher in BUL-WEA (7.2) and CAS-WEA (5.4) than in calves of CAS-CON (2.8) and BUL-CON (2.9) groups (P<0.05). From days 1 to 3 vocalizations decreased in all groups. CAS-CON and BUL-CON animals spent 20% lying on day 1 after weaning compared with 40% in CAS-WEA and BUL-WEA calves (P<0.05). The haptoglobin concentration decreased during the first 5 weeks after weaning in all groups independent of the castration, weaning group or its interaction (P>0.05). WEA groups showed an increased average daily gain (ADG) during weeks 0 to 3 and a reduced ADG during 4 to 7 weeks in comparison with CON animals. At slaughter, bulls were about 80 kg heavier than castrates and had a superior dressing percentage and carcass classification (P>0.05). In conclusion, weaning had a greater effect on the number of vocalizations, standing/walking and lying behaviour and ADG compared with Burdizzo castration. In comparison with undertaking the procedures separately, concurrent castration and weaning neither affected behaviour and haematological parameters nor impaired performance. There was no evidence that the concurrent application of both treatments markedly increased the stress response compared with their application at intervals of a few weeks.     

Effect of daily concentrate intake at weaning on performance of Belgian Blue double-muscled rearing calves

Weaning at a different daily concentrate intake was investigated during a 140-d experimental period, using 54 male and 68 female newborn Belgian Blue double-muscled animals. They were divided into three comparable groups and received milk at 10% of their birth weight up to weaning. Concentrate was levelled off at a maximum daily intake of 3 kg, while grass hay was freely available. Weaning occurred at a daily concentrate intake level (CL) of 0.5, 0.75 and 1.0 kg, respectively. Weaning at an increased CL prolonged the milk-feeding period by 13.1 and 14.6 days, and resulted in a higher pre- and post-weaning growth rate (p < 0.05). Daily gain during the entire experimental period averaged 0.84, 0.85 and 0.88 kg for the respective groups (p = 0.065). Daily concentrate intake was not different among groups, with only a small effect of CL on intake around weaning. Early weaning resulted in a significant reduction of hay intake (p = 0.032). Total daily net energy intake increased slightly with a higher CL at weaning, so that energy conversion was slightly improved, amounting to 17.7, 17.6 and 17.4 MJ/kg gain, respectively. Energy balance during the first week after weaning was negative for CL 0.5 kg (-22%), while it was close to 0 for CL 0.75 kg (-2%) or positive for CL 1.0 kg. Most effects of CL at weaning were similar for males and females, but male calves tended to have a higher intake and a faster growth rate than females. It can be concluded that weaning should be delayed until Belgian Blue double-muscled calves consume at least 0.75 kg per day or more for reasons of welfare, although performance was hardly improved by weaning at a daily concentrate intake of more than 0.5 kg per day.     

Extraction methods in bovine obstetrics: comparison of the demanded energy and importance of calf and traction method in the variance of force and energy

In a previous study we could demonstrate that in terms of the required forces alternate traction is preferable to simultaneous traction for the obstetrical delivery of calves. The aims of this study were to examine the required energies for delivery of calves and to compare the effects of the factors of calf and traction method on the forces and energies required for the delivery. In a biomechanical in vitro model 12 stillborn Holstein-Friesian calves were pulled through the pelvic specimen of a cow at a controlled speed using two electric motors. Traction was applied simultaneously (ST) to both legs or alternately (AT) to one leg at a time to advance it 10 cm (AT 10) or 5 cm (AT5). Energies on each limb were measured digitally using load cells. The lowest energy for the entrance of the elbows in the pelvis was necessary using AT10 (19.9 ± 7.2 kJ, P < 0.05). In contrast, for the entrance of the chest, AT10 (104.9 ± 24.7 kJ) demanded 9% (P < 0.01) and 16% (P < 0.001) more energy than AT5 (96.7 ± 21.0 kJ) and ST (90.5 ± 24.9 kJ), respectively. Simultaneous traction tended to be better than AT5 (P = 0.09). Variance component estimates revealed that the factor calf contributed the main effect to the emerging forces and required energy. The traction method was responsible for up to 13% of the variance in most of the cases, but it accounted for 42% of the variance regarding the forces on the lower limb as the chest entered the pelvis. Based on these findings, the decision of the clinician whether or not to perform a manual traction should depend mainly on the calf. However, when such a decision has been made, alternate limb traction, 10 cm at a time, should be used until both elbows have entered the pelvis and a simultaneous traction should then be applied to complete extraction of the chest.