Body measurements of newborn calves and relationship of calf shape to sire breeding values for birth weight and calving ease

Body measurements on Angus- (n = 374) and Polled Hereford-sired (n = 438) calves were used to quantify calf shape via multivariate factor analysis, and measurements on Polled Hereford-sired calves were further used to investigate relationships between calf shape and sire expected progeny differences (EPD) for birth weight and first-calf calving ease. Calf birth weight, head circumference, shoulder width, hip width, heart girth, cannon bone circumference and length, and body length were recorded at 24 h postpartum. Sire birth weight EPD was positively associated (P less than .05) with all calf measures but only with head and cannon circumference after adjustment for phenotypic birth weight and gestation length. Thus, at constant birth weight, calves from higher birth weight EPD bulls tended to have larger cannon and head circumferences. Calving ease EPD was negatively related (P less than .05) to all calf measures except shoulder width. After adjustment for birth weight, only cannon circumference was associated with calving ease EPD, and this effect was removed by additional adjustment for birth weight EPD. Thus, at constant birth weight, bulls with higher EPD for calving ease sired calves with smaller cannon circumference, but at constant birth weight EPD, body measures were not associated with calving ease EPD. Factor analysis defined underlying skeletal width and frame components of shape (independent of birth weight) for both sire breeds. Calf shape differed among sires and was in part explained by birth weight EPD. No additional variation in shape was explained by calving ease EPD. Calf shape seemed to add no information for prediction of dystocia to that provided by birth weight EPD.     

Effects of Tuli,Senepol, Brahman,Angus, and Polled Hereford Sire Breeds on Birth and Weaning Traits of Offspring

Progeny (n = 861) of tropically adapted breeds [Tuli (TU), Senepol (SE), and Brahman (BR)] and temperate breeds [Angus (AN) and Polled Hereford (HP)] were evaluated for birth and weaning traits in each of 5 yr. Multiparous crossbred cows representing three genetic types [British (Bt), ½BR½Bt, and ¾Bt¼BR] were mated to AN, HP, TU, SE, and BR sires, with the exception that BR sires were not mated to ½BR½Bt cows. Calving season was January through early March. Following calving, cows were provided bermudagrass hay and bahiagrass hay and had limited access to rye and ryegrass pastures. Cow and calf pairs grazed bermudagrass and bahiagrass pastures as available until weaning without access to creep feed. Male calves were castrated at birth and were not implanted. Data included birth weight, cannon bone length at birth, weaning weight, weaning hip height, ADG from birth to weaning (ADGBW), ADG from birth to April (ADGBA), ADG from April to weaning (ADGAW), and weight per day of age (WDA). Data were analyzed by PROC Mixed using a model that included calf genetic type, calf sex, calf birth day of year, and calf genetic type × calf sex interaction. Random effects were cow age, birth year, and sire and dam of calf. Calf genetic type and calf sex were significant sources of variation for all characteristics. Linear contrasts revealed that BR-sired calves were heavier at birth, had longer cannon bones at birth, and were taller at weaning (P<0.01). Tuli- and SE-sired calves were similar to AN- and HP-sired calves for birth weight, cannon bone length at birth, and weaning hip height. Angus-, HP-, and BR-sired calves were heavier at weaning compared with TU-sired calves, and SE-sired calves were intermediate for weaning weight (P<0.01). In conclusion, the TU-sired calves were smaller at birth and at weaning when compared with BR-sired calves. The TU- and SE-sired calves appear to offer more moderate size and growth rate through weaning than do the BR-sired calves.     

STUDIES ON DYSTOCIA AND BIRTH WEIGHT IN ANGUS HEIFERS CALVING AT TWO YEARS OF AGE

A trial is described in which groups of Angus heifers mated as yearlings were maintained on two widely differing nutritional levels during the last third of gestation in order to study effects on birth weight of calves and dystocia. The different nutritional levels produced a 5 lb difference in birth weight of calves (P < 0.01). As the calving season advanced the mean calf birth weight increased by 1.4 lb every ten days (P < 0.01). Heifers that suffered dystocia had calves 7 lb heavier and pelves 15.6 sq cm smaller than heifers calving normally (P < 0.01). Following observations on the birth process it was concluded that uncomplicated birth is complicated within two hours following the appearance of the amniotic sac.     

Fetal growth of beef calves. II. Effect of sire on prenatal development of the calf and related placental characteristics

Fifteen Hereford and 47 crossbred heifers were allotted by breed and body weight to be artificially inseminated to one of two Angus sires selected for progeny birth weights (L = low; H = high). Forty-two of the heifers were randomly assigned to be slaughtered at 200, 215, 230, 245 or 260 d of gestation for measurement of fetal and placental characteristics. Twenty heifers were allowed to go to term and five calves from each sire group were randomly assigned to be euthanized and dissected within 24 h after birth. Sire differences in birth weight (BW) and dystocia score (32.9 vs 35.4 kg; 1.8 vs 3.1, L vs H sires, respectively) existed (P less than .01), and there was a sire effect (P less than .01) for fetal calf weights (FW) and eviscerated calf weights (EW). However, there was a sire X calf sex interaction for BW (P less than .05), EW (P less than .01), FW (P less than .01), femur length (P less than .05), heart weight (P less than .05), kidney weight (P less than .01) and pituitary weight (P less than .01). Weight differences suggested these interactions were a result of the relationship of the organ weights to fetal body weights and the interaction effects on calf weights resulted from limitations in the maternal environment which restricted growth of H-sired male calves in utero. Sire X fetal age interaction effects were all nonsignificant (P greater than .10) except for cerebrum weight. This finding indicates that fetus and calf growth rates were parallel for the L and H sires. A sire effect was found for biceps (P less than .01) and liver weights (P less than .01), but not for cerebrum weights (P greater than .10). Increasing weight due to fetal age was attributed to hypertrophy for the cerebrum (P less than .05) and liver (P approximately equal to .01), while the biceps increased (P less than .05) by both hypertrophy and hyperplasia, as determined from deoxyribonucleic acid and protein analyses. All measured fetal organ weights except heart, when expressed as a ratio with EW, decreased (P less than .05) with increasing fetal age. Brain (cerebrum + cerebellum):liver weight ratios were higher (P less than .01) in L-sired calves (.32 vs. .28) than in H-sired calves. Total placentome weight (b' = 91; P less than .01) and placental fluid volume (b' = .32; P less than .01) were highly associated with FW, accounting for 84% of the variation in FW.(ABSTRACT TRUNCATED AT 400 WORDS)     

Reproductive rates, birth weight, calving ease and 24-h calf survival in a four-breed diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle

Calving and weaning rates, birth weight, calving ease, and 24-h calf survival were evaluated in a four-breed diallel of Simmental (S), Limousin (L), Polled Hereford (H) and Brahman (B) beef cattle in five calf crops. Limousin dams tended to have the highest calving and weaning rates because they were able to have heavier calves with less calving difficulty and higher survival rates. Brahman-sired calves were the heaviest at birth (P less than .05) and B dams produced the lightest calves (P less than .001). Lower birth weights tended to be the limiting factor on survival of these calves. A linear comparison among means to evaluate purebred, additive, maternal and specific combining ability effects showed most of the reduction in birth weight from B dams was due to maternal effects. Breed of dam accounted for a higher proportion of variation in calving ease than did sire breed. Simmental sires had significantly heavier calves at birth and S and H dams tended to have more calving difficulty and lower survival rates. Heterosis for these traits was generally not significant. Correlations were generally positive and significant for birth weight and calving ease, but were more variable for birth weight and survival. Linear regressions of calving ease on birth weight both within years and within dam-breed-year subclasses were very similar in that the association of these two traits was reduced as dam age increased.     

Heterosis, maternal and direct effects in double-muscled and normal cattle: I. Reproduction and growth traits

Data from a two-breed group diallel experiment involving double-muscled (DM) and normal (N) cattle were analyzed to evaluate the importance of heterosis, maternal and direct effects for reproduction and growth traits. The DM cattle were from a composite of primarily Angus, Charolais, Galloway and Hereford breeds, and N cattle were crossbred cattle with at least 50% Hereford breeding. The data comprised a total of 491 matings and 389 calvings in four breeding seasons. Records on calving performance, calving date, calf crop born and weaned, sex ratio of progeny and weight of calves were analyzed using least squares procedures. Significant heterosis of 5 to 12% was observed for all the calf crop and growth traits, except for birth weight. Heterosis resulted in 24% reduction in the incidence of dystocia and perinatal calf mortality (P less than .05). The significant heterosis was due mainly to poor production in DM X DM crosses. The DM cows were superior (P less than .05) to N cows in reciprocal crossing (maternal effect) for all the calf crop traits, but had higher incidence of calving difficulty and a higher proportion of male progeny. Significant direct effect was observed for all the traits except calving date and sex ratio among progeny. The N sires were superior for all the calf crop traits and caused less incidence of dystocia and perinatal mortality compared with the DM sires. Significant differences were obtained between the straightbreds for all the traits except calving date. The N straightbreds were superior to the DM straightbreds for all the significant traits.     

Factors affecting dystocia and early calf mortality in Angus cows and heifers.

Calving performance records (965,417) from purebred American Angus herds throughout the United States were used to study dystocia and early calf mortality during the period from 1972 to 1985. A sample of 53 (n = 83,467) herds was used to establish reasonable limits on the expected frequency of dystocia and mortality within and among herds that have good reproductive management programs and to verify the frequencies of scores in all other herds (n = 4,130) reporting calving performance information. The data were analyzed by logistic regression models. Dystocia and perinatal mortality, to a lesser extent, were found to be more frequent in heifers than in cows. The odds of unassisted births vs births with major difficulty were 11.58 times greater in cows than in heifers. In heifers, the odds of an unassisted birth increased with age of dam and decreased with birth weight of calf. At a baseline age of 22 mo the odds of an unassisted birth for calves weighing 30 and 40 kg were .13 and .02 times lower than the odds for calves weighing 20 kg. Alternately, at 29 mo, the odds of an unassisted birth for heifers producing a 20-kg calf were 4.53 times greater than at 22 mo. Survival of calves to 24 h in heifers was primarily affected by birth weight. Heifers producing calves at intermediate weights of 29 kg had higher odds of producing live calves at all ages. Considering all heifers calving at 22 to 29 mo relative to 20-kg calves, the odds for survival to 24 h were 3.83 times greater for 29-kg calves and lower by a factor of .52 for 40-kg calves.     

鲁中肉羊初生体尺体重的遗传参数估计

为估计鲁中肉羊初生重、体高、体长、胸宽、胸深、胸围和管围的遗传参数,利用2018年上半年出生的611只鲁中肉羊的初生体尺体重数据,采用AI-REML (Average information restricted maximum likelihood)算法,借助DMU软件分析以产羔数为固定效应、个体加性遗传效应为随机效应的多性状动物模型。结果表明:鲁中肉羊初生重、胸宽、胸深、体高、体长、胸围和管围的遗传力分别为0.16、0.10、0.22、0.44、0.43、0.46和0.52,各性状之间遗传相关为-0.517～0.773,表型相关为-0.197～0.503。说明鲁中肉羊初生重、胸宽和胸深为低遗传力性状,体高、体长、胸围和管围为中等遗传力性状。     

The effect of dystocia on physiological and behavioral characteristics related to vitality and passive transfer of immunoglobulins in newborn Holstein calves

The objective of this study was to examine the effect of calving difficulty or dystocia on the vitality of newborn calves and its association with blood pH, the apparent efficiency of immunoglobulin G (IgG) absorption (AEA), and weight gain. A total of 45 calving events (N = 48 calves) were monitored from the first sight of fetal membranes. All calves were assessed at the time of first attaining sternal recumbency (SR), at 2 and 24 h, and at 7 and 14 d of age. Measurements included time to SR, rectal temperature, respiration and heart rate, analysis of blood gases and other blood measures, suckling response, time to standing, passive transfer of IgG, and weight gain. Calves were separated from their dam 2 h after birth and fed a commercial colostrum replacer containing 180 g of IgG by esophageal tube feeder. Calves born following dystocia had lower venous blood pH and took longer to attain SR and attempt to stand than those born unassisted. Duration of calving interacted with the number of people required to extract the calf by pulling as a significant predictor of pH at SR. No association was found between pH at SR and AEA. However, reduced AEA was found in calves that were female and in calves that did not achieve SR within 15 min of birth. A longer calving duration, being born in July or August rather than June, and a shorter time spent standing in the first 2 d of life were significantly associated with reduced weight gain to 14 d. It was concluded that factors at calving impact the physiology, vitality, and subsequent weight gain of newborn calves.     

Characteristics of calves produced with sperm sexed by flow cytometry/cell sorting

The objectives of this study were to determine whether calves produced by sexed sperm differed from controls and to what extent the sex ratio of calves was altered by the sexing procedure. Data were collected from 1,169 calves produced from sperm sexed by flow cytometry/cell sorting after staining with Hoechst 33342, and 793 calves produced from control sperm during breeding trials between 1997 and 2001. Least squares ANOVA were completed using factors of treatment (sexed vs. control sperm), 19 management groups from 13 field trials, and calf sex. Responses analyzed include gestation length, birth weight, calving ease, calf vigor, weaning weight, abortion rate, and death rates (neonatal and through weaning). No significant difference was observed for any response due to treatment or treatment interactions (P > 0.10). Therefore, calves produced from sexed sperm grew and developed normally both pre- and postnatally. A neurological disorder was observed in four control calves and one sexed calf from one farm. No gross anatomical abnormalities were reported for any calves in the study. Differences were observed for all responses among management groups (P < 0.03 for abortions and P < 0.01 for all other responses). Heifer and bull calves differed (P < 0.001) in gestation length (278.4 and 279.6 d), birth weight (32.8 and 35.2 kg), calving ease (1.15 and 1.30), and weaning weight (233 and 247 kg). Gestation length did not affect characteristics of calves. The sex ratio at birth of calves from unsexed control sperm was 49.2% male. Sexing accuracy of X-sorted sperm was 87.8% female calves, and Y-sorted sperm produced 92.1% male calves. Flow cytometry/cell sorting can be used to preselect sex of calves safely with approximately 90% accuracy.     

Effect of tropically adapted sire breeds on preweaning growth of F1 Angus calves and reproductive performance of their Angus dams

The objective of this study was to determine the effect of tropically adapted sire breeds on preweaning growth performance of F1 calves and on reproductive performance of their Angus dams. Angus (A) cows were bred in two consecutive years (1992 and 1993) by AI using semen from Brahman (B; Bos indicus; n = 10), Senepol (S; Bos taurus; n = 10), and Tuli (T; Sanga; n = 9) bulls. A total of 82 B x A, 85 S x A, and 91 T x A calves were born. The statistical model included the fixed effects of year, sire breed, calf sex, sire breed x calf sex, and cow parity and the random effect of sire within sire breed. Birth weight, weaning weight, 205-d adjusted weaning weight, ADG from birth to weaning, and hip height at weaning were greater (P < .001) for B x A calves than for S x A or T x A calves. Greater differences were detected between sexes for B x A than for S x A and T x A (for all traits sire breed x calf sex, P < .05). Sire breed affected (P < .01) the percentage of unassisted calvings (B x A, 87%; S x A, 98%; and T x A, 100%) and tended (P < .10) to affect the percentage of calves that survived until weaning (B x A, 90%; S x A, 94%; and T x A, 98%). Sire breed of calf did not affect (P > .10) length of gestation, and sire breed did not affect the interval from calving to first observed estrus or pregnancy in Angus dams. These results demonstrate that preweaning growth performance of B x A calves was greater than that of either S x A or T x A calves. However, use of Brahman sires on Angus dams led to calving problems and tended to reduce the percentage of calves that survived until weaning. Thus, heavier weaning weights of B x A calves would be an advantage for cow-calf producers marketing calves, but heavier birth weights and calving difficulty attributed to Brahman sires would be a disadvantage.     

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.     

凉州区肉牛繁殖技术试验示范与推广研究

[目的]为筛选出适合凉州区肉牛繁殖的新模式。[方法]选择夏洛莱（XL）、利木辛（LM）、安格斯（AG）成年种公牛生产冻精,在西门塔尔和本地黄牛杂交一代（西本F1）成年母牛上实施人工授精,对杂交犊牛分月龄进行外貌体尺测定。[结果]XL冻精与西本F1代的后代体重、体高、体斜长、胸围、管围等生长指标均高于LM和AG后代指标。试验2方法是选择XL、LM、AG成年母牛生产冻胚,在成年母牛上实施胚胎移植,犊牛出生后进行外貌体尺测定。结果是：夏洛莱胚胎移植后代牛初生重、6月龄、12月龄体重、体高、体斜长、胸围、管围均高于利木辛与安格斯牛杂交后代（P〈0.01）。试验3方法是选择西杂F1和F2代母牛,用引进的XM（西门塔尔）牛X性控冻精实施人工授精,犊牛出生后统计相关数据。结果是：三组共授配母牛138头,情期妊娠75头,情期平均受胎率为54.1%,平均母犊率为90.3%。[结论]夏洛莱品种改良西杂一代牛后代生长发育比其余品种好;实施胚胎移植后,夏洛莱品种胚胎移植后代牛比其余品种在凉州区生长适应性强,适宜在该环境条件下生长;西门塔尔牛性控冻精的配种试验是成功的,是生产母犊的较好方法。     

Calving and weaning characteristics of Angus-, Gray Brahman-, Gir-, Indu-Brazil-, Nellore-, and Red Brahman-sired F1 calves

Calving and weaning data from crossbred calves sired by five Bos indicus breeds and one Bos taurus breed were evaluated. Data included calving and weaning records of F1 calves out of multiparous Hereford cows and sired by Angus, Gray Brahman, Gir, Indu-Brazil, Nellore, and Red Brahman bulls. At calving, Angus-sired calves had shorter gestations and lower (more desirable) calving ease scores and were smaller than Bos indicus-sired calves. Among the Bos indicus crosses, Gir calves had the shortest gestations, lowest calving ease scores, lightest birth weights (P less than .05), and smallest cannon bone lengths and heart girths. Nellore calves had the longest gestations (P less than .05) and largest heart girths. Calves by Indu-Brazil sires had the highest calving ease scores, highest birth weights (P less than .05), and greatest cannon bone lengths (P less than .05). Gray Brahman- and Red Brahman-sired calves were similar and intermediate for all calving characters. At weaning, Angus-sired calves had gained slightly faster than the Gir crosses and weighed more but were shorter at the hip than Gir crosses. Gir calves gained the least preweaning, weighed the least, and were shortest at weaning of the Bos indicus crosses. The Nellore and Indu-Brazil crosses were intermediate in preweaning gain and weaning weight to the Gir and the Red and Gray Brahman but were tallest at weaning. Gray Brahman and Red Brahman calves gained the most and were heaviest at weaning but were not as tall as the Nellore and Indu-Brazil.     

Analysis of gestation length in American Simmental cattle

Records of gestation length (71,461) for Simmental cattle were distributed with mean 284.3 d and standard deviation 5.52 d. Gestation length was found to increase with percent Simmental and was 1.9 d longer for calves born to mature dams than for those born to heifer dams. Bull calves experienced gestation lengths 1.5 d longer than heifer calves. Sire, maternal grandsire, residual and total variances were estimated to be 2.42, .58, 22.78 and 25.78 d2, respectively, by Henderson's Method III. Heritability of gestation length was calculated to be .374 from the sire variance and .09 from the maternal grandsire variance. Direct additive genetic variance was considered to be of greater importance than maternal additive genetic variance. Correlations between the evaluations of sires for gestation length and heifer calving ease, birth weight and weaning weight were .26, .26 and .13, respectively.     

安格斯肉牛冻精与隔年产犊牦牛杂交改良效果分析

通过对上年未产犊牦牛采用补饲与同期发情处理技术,并采用安格斯肉牛细管冻精开展牦牛杂交,出生的犏牛犊采用犊牛培育技术,对不同培育条件对犏牛犊牛生长发育的影响,研究结果表明,采用上年未产犊母牦牛补饲技术,与对照组相比,试验组隔年产犊母牦牛的发情率、受胎率、产犊率及犊牛成活率分别为86.67%、82.23%、78.34%和96.46%,分别提高22.84%、27.59%、33.03%和7.62%,差异显著(P<0.05)。采用犏牛犊牛培育技术,与传统对照组相比,犊牛培育组和培育对照组公、母犏牛初生的体高、体斜长、胸围、管围体重明显增加,差异显著(P<0.05)。上年未产犊母牦牛补饲与同期发情处理技术结合犏牛犊牛培育技术,显著提高其杂交一代犏牛的生长发育速度,提高犊牛的繁殖成活率。     

新疆褐牛的体尺、体重对产奶量的影响

本试验在新疆畜牧厅乌鲁木齐种牛场选择新疆褐牛 121 头,对其出生重、体高、胸围、管围、体斜长与产奶性能的资料进行分析,研究新疆褐牛的出生重、体高、胸围、管围、体斜长与产奶性能的相关性.结果表明:新疆褐牛的初生重对产奶量有显著的影响(P相似文献   

Twinning in cattle: III. Effects of twinning on dystocia, reproductive traits, calf survival, calf growth and cow productivity

An evaluation of natural twinning in beef cattle revealed that cows birthing twins had shorter (P less than .01) gestation lengths, more (P less than .01) retained placentas, more (P less than .01) dystocia, more (P less than .01) days to estrus, lower (P less than .01) conception rates and more (P less than .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of calves reared (1 vs 2) in cows birthing twins. Survival at birth was greater (P less than .01) for single- than for twin-born calves, but twins and singles did not differ (P greater than .05) in postnatal survival. When dystocia was experienced, calf survival at birth was 95% vs 73% for singles vs twins compared with 99% vs 92% when no dystocia was experienced. Calves born twins were lighter (P less than .01) at birth, 100 d and 200 d, but twins and singles did not differ in postweaning gains. Total calf weights at 100 d per cow calving were 12% greater (P less than .01) in cows birthing twins vs singles when twin calves reared by foster dams were excluded. The potential increase in cow productivity for total calf weight at 100 d is 40% if calf survival rates of twins with dystocia relative to survival rates of twins without dystocia were comparable to survival rates of singles with and without dystocia, and if cows birthing twins were fed and managed to obtain conception rates equal to those of cows birthing singles. Identification of cows gestating twins to provide for their higher prepartum nutritive requirements and calving assistance at parturition is necessary to make twinning in cattle an economically viable technology.     

Factors Affecting Dystocia in Cattle

The paper reviews the various factors affecting dystocia in cattle. It is based mainly on the recent studies found in the literature of the subject but refers occasionally to some older papers as well. The factors are grouped into four main categories: direct factors, phenotypic factors related to calf and cow, non-genetic and genetic factors. The first group includes malpresentations and uterine torsion. The second one includes: calf birth weight, multiple calvings, perinatal mortality, cow pelvic area, cow body weight and body condition at calving, gestation length. The non-genetic factors are: cow age and parity, year and season of calving, place of calving, maintenance practises, disorders, calf sex and nutrition. Other non-genetic factors are the level of hormones in the periparturient period, in vitro production of embryos and embryo cloning. Finally, the genotypes of cow, bull and calf, inbreeding, muscular hypertrophy, selection and quantitative trait loci form the fourth group of genetic factors.     

犊牛早期(3月龄)断奶生长发育情况分析

[目的]探索犊牛早期(3月龄)断奶的可行性,为推广犊牛早期(3月龄)断奶技术提供依据,增加养殖企业的经济效益成本。[方法]试验选取出生后3月龄的西门塔尔犊牛,进行断奶饲养,测量断奶后不同日龄的体重及体尺指标,分析其生长发育情况,并对体重及体尺进行相关性分析。[结果]西门塔尔犊牛断奶后增重快速,断奶后90天,犊牛平均体重达到269.67kg,断奶后平均总增重达到101.54kg,全程日均增重为1128.22g。断奶后90天与断奶后30天比较,体斜长、体高、胸宽、胸深、胸围、腹围、臀围均呈现增加的趋势,其中增长较快的是腹围,其次是胸围,分别增加了19.0cm,14.67cm。体重与体斜长、体高、胸宽、胸深、胸围、腹围、臀围均呈正相关,其中体重与体斜长、体高、胸深、胸围、腹围呈极显著相关(p<0.01)。[结论]犊牛早期(3月龄)断奶后犊牛生长发育情况较好,犊牛早期(3月龄)断奶具有较强的可行性,可大范围推广。