纯种和牛快速扩繁关键技术研究

为达到快速扩繁纯种和牛的目的,试验从供体牛高强度超数排卵、胚胎性别鉴定及不同品种受体牛移植对产犊、妊娠期和犊牛初生重的影响进行研究。结果表明,纯种和牛连续超排9次,每次间隔30 d,第2次头均回收胚数22.78枚,显著高于第5~9次结果（P< 0.05）,其余各组之间无显著差异（P> 0.05）;第1~3次头均可用胚数分别为8.67、13.78、8.56枚,组间无显著差异（P> 0.05）,第2次头均可用胚数显著高于第4~9次头均可用胚数（P< 0.05）,极显著高于第7、9次头均可用胚数（P< 0.01）。性别鉴定胚胎和常规胚胎移植妊娠率和产犊率差异均不显著（P> 0.05）,性别鉴定胚胎的母犊率为95.56%。西门塔尔杂交牛受体产犊率高于和牛杂交牛、荷斯坦奶牛受体,但差异不显著（P> 0.05）。和牛杂交牛受体妊娠期极显著高于西门塔尔杂交牛和荷斯坦奶牛受体（P< 0.01）,西门塔尔杂交牛和荷斯坦奶牛之间差异不显著（P> 0.05）;西门塔尔杂交牛受体所产和牛母犊初生重显著高于和牛杂交牛受体（P< 0.05）,极显著高于荷斯坦奶牛受体（P< 0.01）,3个品种受体牛产和牛公犊初生重之间差异不显著（P> 0.05）;同一品种受体牛其产公、母犊牛的妊娠期及初生重均相近。     

澳洲和牛超数排卵与体内胚胎生产的影响因素研究

旨在研究不同发育阶段(青年和经产牛)、同期方法、促卵泡素(follicle-stimulating hormone,FSH)剂量、超排次数等因素对澳洲和牛供体超数排卵(简称超排)和体内胚胎生产效率的影响.本试验共选用38头青年和牛(16?20月龄)和42头经产和牛(胎次=1)进行超排处理,分别统计每头供体牛回收的总胚胎...     

影响荷斯坦牛妊娠期长短的因素分析

[目的]为探究不同因素对荷斯坦牛妊娠期长短的影响,以期进一步改善奶牛繁殖性能.[方法]研究利用一般线性模型对江苏省某奶牛场2017-2019年20 589条产犊记录进行分析,探究不同胎次、产犊季节、犊牛初生重、犊牛性别及是否产双犊和是否使用性控冻精对荷斯坦牛妊娠期长短的影响.[结果]胎次、产犊季节、犊牛初生重、是否产双...     

和牛超数排卵影响因素的研究

为探讨和牛超数排卵的影响因素,试验采用4 d 8次注射Folltropin-V的超数排卵方法,在不同季节对不同父系和牛供体牛群超数排卵1～10次.结果表明:①春季、夏季、秋季和冬季超数排卵和牛分别获得7.1、7.8、8.3、7.7枚头均胚胎数和5.2、4.7、5.2和5.2枚头均可用胚胎数,差异均不显著(P>0.05);夏季和秋季超数排卵和牛分别获得3.2和3.1枚头均不可用胚胎数,显著高于春季获得的1.9枚头均不可用胚胎数(P<0.05);②和牛供体重复超数排卵1～10次,头均胚胎数、头均可用胚胎数和头均不可用胚胎数分别为7.5～9.3、4.6～6.1和2.7～3.4枚,差异均不显著(P>0.05);③父系为WESFA0107的供体牛群超数排卵获得11.1枚头均胚胎数,显著高于父系为GOSFZ0302、BYWFA0015、BYWFY0342、BYWFY0350和TFWFW06290供体牛群超数排卵获得的头均胚胎数(P<0.05),6.2枚头均可用胚胎数显著高于父系为BYWFY0350的供体牛群超数排卵获得的3.6枚头均可用胚胎数(P<0.05),3.3枚头均退化胚胎数显著高于父系为BYWFA0015、BYWFY0350和TFWFW06290的供体牛群超数排卵获得的1.8、1.1和1.7枚头均退化胚胎数(P<0.05),1.6枚头均未受精卵数显著高于其他6个父系供体牛群超数排卵获得的头均未受精卵数(P<0.05);父系为BYWFY0350的供体牛群超数排卵获得的5.3枚头均胚胎数和3.6枚头均可用胚胎数在7个不同父系供体牛群胚胎生产中均为最少.因此,避开夏季高温季节,增加超数排卵次数同时选择超数排卵反应好的同一父系供体能够提高和牛超数排卵效率.     

Birth weight and gestation length of Japanese black calves following transfer of embryos produced in vitro with or without co-culture.

Birth weight and gestation length of calves following the transfer of in vitro produced (IVP) embryos with or without co-culture of cumulus cells, were compared to those produced in vivo (IVD). Spermatozoa from one Japanese Black bull were used for both IVP and IVD. IVP embryos were produced using two types of culture method: 1) co-culturing with cumulus cells in TCM 199 supplemented with calf serum (IVP-Co), and 2) non-co-culturing without cumulus cells in CR1aa supplemented with BSA / calf serum (IVP-NON-Co). Both IVP and IVD embryos were transferred non-surgically to Holstein recipients on day 7+/-1 of the estrous cycle. Birth weight and gestation length of half-sib single calves were analyzed. No differences were observed in birth weight and gestation length between IVP-Co and IVP-NON-Co calves (31.0 kg and 31.8 kg, and 291.9 days and 291.0 days, respectively). However, the birth weight of the IVP-Co and IVP-NON-Co calves was significantly higher than that of the IVD calves (P<0.01). Gestation length of the IVP-Co and IVP-NON-Co calves was also significantly longer than that of the IVD calves (P<0.01).     

不同因素对高产荷斯坦奶牛体内性控胚胎生产效率和质量的影响

[目的]试验旨在探讨不同种类的促卵泡素(FSH)超数排卵处理、不同精液类型人工输精处理以及不同季节等前处理方式对高产荷斯坦奶牛体内性控胚胎生产效率的影响,为高产胚胎牛后代的繁育做出贡献。[方法]试验选取208头优质供体牛使用加拿大(Folltropin-v)和比利时进口的促卵泡素(FSH)进行超排,性控冻精和性控鲜精进行人工输精,春(3—5月)、夏(6—8月)、秋(9—11月)、冬(12—2月)四季进行胚胎生产。[结果]结果表明,使用产地为加拿大(Folltropin-v)促卵泡素进行超数排卵头均可用胚胎数和I级胚胎数(包括桑葚胚I级、囊胚I级)均显著高于比利时(P<0.05);通过使用性控冻精和性控鲜精对供体牛进行人工输精头均可用胚胎数分别为和I级胚胎数差异均不显著(P>0.05);春、夏、秋、冬四季进行胚胎生产头均可用胚胎数和I级胚胎数夏季均显著低于其他三季(P<0.05)。[结论]因此,使用加拿大促卵泡素(Folltropin-v)超数排卵、性控冻精进行人工输精避免在夏季进行胚胎生产可获得质量较高的高产荷斯坦奶牛体内性控胚胎。     

激素剂量、超排间隔及重复超排次数对和牛重复超排效果的影响

试验旨在探讨激素剂量、超排间隔及重复超排次数对和牛重复超排效果的影响，为建立稳定、高效的和牛供体重复超排方案提供依据。本试验共选取63头15~18月龄的和牛供体母牛进行超排处理，其中17头和牛供体随机分成2组，分别以200、200、200 mg的FSH注射总剂量和200、220、240 mg的FSH注射总剂量进行3次重复超排，每次超排间隔30 d，研究激素剂量对和牛重复超排的影响；24头和牛供体随机分成3组，每组分别以60、45、30 d的超排间隔，每次200 mg的FSH注射总剂量进行3次重复超排，研究超排间隔对和牛重复超排的影响；22头和牛供体采用每次200 mg的FSH注射总剂量进行连续7次重复超排，每次超排间隔30 d，研究重复超排次数对和牛重复超排的影响。结果显示，采用FSH注射总剂量为200、220、240 mg获得的头均胚胎总数和头均可用胚胎数显著高于每次均为200 mg的FSH注射总剂量（P<0.05）；与超排间隔60 d组相比，超排间隔45 d组获得的头均可用胚胎数显著降低（P<0.05），而超排间隔30 d组获得的头均可用胚胎数也降低，但差异不显著（P>0.05）；重复超排在6次以内，获得的头均可用胚胎数无显著差异（P>0.05）。结果表明，注射FSH总剂量为200、220、240 mg连续超排3次的超排效果优于注射FSH总剂量为200、200、200 mg组；超排间隔越长，越有利于母牛生殖道的恢复，获得的可用胚胎数越多，但超排间隔30 d，也可获得良好的超排效果；高强度重复超排以30 d为超排间隔，超排5~6次为宜。     

和牛超数排卵及胚胎移植效果观察

为了研究和牛超数排卵和胚胎移植的效果,试验以和牛作供体,荷斯坦青年母牛作受体,采用PG+FSH方案对7头和牛供体进行超数排卵处理,用非手术法取胚并进行鲜胚移植。结果表明：采用PG+FSH方案头均获得胚胎数为(11.29±4.86)枚,可用胚胎(5.86±3.27)枚(A级和B级);鲜胚移植(A级和B级)妊娠率为51.22%。说明采用该方案对和牛供体进行超数排卵,并进行鲜胚移植的效果较为理想。     

体细胞克隆牛0～12月龄生长的测定研究

通过对5头体细胞克隆母犊牛及其同期自然繁殖出生的荷斯坦母犊牛初生期、6月龄、12月龄的体重、体尺指标测定,初步分析了其生长发育速度的变化规律。结果表明:(1)克隆牛初生重53.67±7.00kg,明显高于自繁奶牛(P<0.01),6月龄体重141.00±16.49kg,明显低于自繁奶牛(P<0.01),12月龄体重302.80±32.17kg,与自繁奶牛基本相当;(2)克隆牛0～6月龄期间平均日增重0.70±0.11kg明显低于自繁奶牛(P<0.01),6～12月龄期间平均日增重0.90±0.12kg,与自繁奶牛基本相当(P>0.05),0～12月龄期间平均日增重0.70±0.11kg,与自繁奶牛基本相当(P>0.05);(3)克隆牛初生体尺指标明显大于自繁奶牛(P<0.01),6月龄体尺指标明显小于自繁奶牛(P<0.01),12月龄体尺指标与自繁奶牛相当(P>0.05);(4)克隆牛0～6月龄期间体尺平均增长明显低于自繁奶牛(P<0.01),6～12月龄期间体尺平均增长明显高于自繁奶牛(P<0.01),0～12月龄期间体尺平均增长明显低于自繁奶牛(P<0.01)。     

日本和牛胚胎移植的试验研究

[目的]为了在我国引进日本和牛这一高等级肉牛品种并迅速扩大纯种日本和牛的数量.[方法]分别采用CIDR+E2法和两次PGF2α法对胚胎移植受体牛做同期发情处理,采用一步细管法冷冻的日本和牛胚胎进行移植,观察妊娠率.[结果]表明,受体牛经CIDR+E2法和两次PGF2α法处理后12～48 h的发情率分别为82.7%和45.9%,两者之间差异显著(P＜0.05),对90枚日本和牛胚胎进行一步细管法管内解冻,然后给62头CIDR+E2法处理和28头两次PGF2α法处理的受体奶牛移植,受胎率分别为43.5%和42.5%,产犊率分别为40.3%和39.3%,两者之间差异不显著(P＞0.05).[结论]经同期发情处理的受体牛,只要其子宫环境及卵巢黄体发育良好,被移植日本和牛胚胎都能正常妊娠和产犊;用日本和牛胚胎对低产奶牛进行移植,经三代纯化即可获得纯种日本和牛.     

用荷斯坦奶牛性控精液生产体内性控胚胎

采用荷斯坦奶牛X性控冻精和超数排卵技术结合生产奶牛性控胚胎,以建立高效、低成本的体内性控胚胎生产方法。研究发现,使用CIDR和Cue-Mate进行奶牛同期发情处理,发情率分别为90.9%和100%(P<0.05),且Cue-Mate的发情时间更加集中;加拿大的FOLLTROPIN-V和中国科学院动物研究所的FSH对奶牛超排效果影响不显著,分别为头均胚胎数10.08枚±8.08枚、头均可用胚胎数2.38枚±3.07枚和头均胚胎数6.57枚±4.31枚、头均可用胚胎数2.00枚±1.88枚,无显著差异(P>0.05);奶牛发情后12h～14h和16h～19h人工授精,分别获得头均胚胎数10.25枚±5.53枚、头均可用胚胎数5.33枚±4.52枚和头均胚胎数10.13枚±6.93枚、头均可用胚胎数5.88枚±6.26枚,无显著差异(P>0.05)。但是未受精胚胎数差异显著(27对7,P<0.05)。     

和牛杂交牛高强度重复超排效果的研究

为研究和牛杂交牛短期内重复超排效果,自2011年6月至2011年8月对100头和牛杂交牛连续进行了3次重复超排。结果发现,3次超排获得回收胚平均数分别为11.65±8.96、13.28±7.69、13.24±8.39枚;可用胚平均数分别为7.52±7.16、8.51±6.94和8.92±6.59枚。试验结果表明,对和牛杂交牛进行间隔为33 d的连续3次超排,能够获得较好的超排效果,且个体差异是影响超排效果的主要因素;育成牛超排有效率稍高于经产牛(P>0.05),但可用胚平均数显著低于经产牛(P<0.05)。     

N-氨甲酰谷氨酸对奶牛超排效果及血液指标的影响

本研究旨在探讨饲喂N-氨甲酰谷氨酸（NCG）对奶牛超数排卵效果及血液生化指标的影响。选取荷斯坦育成牛16头，随机分为2组，每组8头，对照组饲喂基础饲粮，试验组在基础饲粮的基础上饲喂20 g/（d·头）的NCG，采用连续4 d递减注射FSH法测定NCG饲喂时间对供体牛超排效果的影响，分别在3次超排处理的第0、5、9天采集尾根静脉血测定激素指标及血清生化指标。结果表明，①NCG饲喂20 d时（第1次超排），试验组头均回收胚数、可用胚数、退化胚数、未受精卵数与对照组相比差异均不显著（P>0.05）；NCG饲喂50 d时（第2次超排），试验组头均回收胚数显著高于对照组（P<0.05）；NCG饲喂80 d时（第3次超排），试验组头均可用胚数显著高于对照组（P<0.05）；综合考虑3次超排效果，试验组头均回收胚数显著高于对照组（P<0.05）。②NCG饲喂时间对供体牛血清中促卵泡素、促黄体素、孕酮、雌二醇的浓度均无显著影响（P>0.05），说明NCG饲喂时间对奶牛生殖激素的分泌无影响或为次要影响因素，超排效果的变化与生殖激素变化无明显的关联作用。③NCG饲喂时间对供体牛血清中谷草转氨酶的浓度无显著影响（P>0.05）；在NCG饲喂13 d时，试验组供体牛血清中葡萄糖浓度显著高于对照组（P<0.05）；在NCG饲喂34 d时，试验组供体牛血清中尿素氮浓度显著低于对照组（P<0.05）；在NCG饲喂43和69 d时，试验组供体牛血清中一氧化氮浓度显著高于对照组（P<0.05）。综合考虑，在重复3次超排时，每头供体牛每天饲喂20 g NCG，可提高3次连续超排的回收胚数4.98枚及可用胚数1.8枚，进而降低胚胎的生产成本。     

西门塔尔牛、和牛与荷斯坦牛杂种优势预测及实际杂交效果分析

旨在利用覆盖全基因组和性状的特异性SNPs标记预测和牛、西门塔尔牛与荷斯坦牛杂种优势,为牛杂种优势利用和选种选配提供参考依据。本研究分别利用牛Illumina Bovine HD 770 K和GGP Bovine 100 K芯片对464头和牛、1 222头西门塔尔牛和43头荷斯坦牛3个亲本群体进行基因型分型,并通过牛QTLs数据库筛选与目的性状对应的QTLs,对比牛参考基因组映射得到与初生重、周岁重、胴体重性状相关的特异性SNPs;然后构建覆盖全基因组和性状特异性SNPs两种标记状态同源矩阵,通过计算杂交组合亲本间的遗传距离来预测品种间杂种优势,并利用配合力分析验证较优组合的实际杂交效果。结果表明,基于全基因组和性状特异性SNPs计算的各杂交组合遗传距离差异不显著。在全基因组水平上,西门塔尔牛♂×荷斯坦牛♀（S×H）与和牛♂×荷斯坦牛♀（W×H）亲本间杂交组合遗传距离分别为0.346 1和0.338 9;在初生重、周岁重和胴体重性状上,S×H亲本间遗传距离分别为0.343 1、0.348 7和0.336 7,而W×H遗传距离分别为0.337 6、0.340 7和0.329 2;两种SNPs标记计算的遗传距离均为S×H较大,W×H次之。因此,在初生重、周岁重、胴体重性状上,S×H为较优杂交组合。通过分析德系西门塔尔牛♂×荷斯坦牛♀实际杂交群体的配合力,发现10个父系在初生重性状上一般配合力和特殊配合力均为正效应,最高效应值分别达到3.760 9和8.931 2。西门塔尔牛与荷斯坦牛杂交可在初生重、周岁重和胴体重获得较高的杂种优势。     

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.     

Changes of vitamin E status of periparturient dairy cows and newborn calves

Eleven primiparous Holstein Friesian and their crossbred calves (F1, Japanese Black cattle × Holstein Friesian) and 10 multiparous Holstein Friesian and their Holstein Friesian calves were used to evaluate vitamin E status in periparturient period. Plasma α‐tocopherol (α‐toc) concentrations of the multiparous cows were significantly higher than those of the primiparous cows from 60 days before expected calving to 90 days of lactation (P < 0.05). The multiparous cows had a further decrease in the concentrations of α‐toc and total lipid in plasma to the calving than the primiparous cows. Colostrum α‐toc concentrations in multiparous cows were significantly higher than those of the primiparous cows (P < 0.05). Plasma α‐toc concentrations of calves borne by the multiparous cows were significantly higher than those of the primiparous cows at 5 days of age (P < 0.05). Plasma α‐toc concentrations of calves were highest at 5 and 15 days of age in the calves borne by the multiparous and primiparous cows, respectively, and decreased thereafter till 90 days of age. The higher vitamin E status of multiparous cows over primiparous cows might have reflected nutritional composition in the rations. Their calves afforded higher plasma α‐toc levels after birth because of more α‐toc transfer via placenta and more α‐toc secretion in the colostrums thereafter. Plasma α‐toc concentrations of the calves might have decreased as the calves became dependent upon the solid feed of low vitamin E content.     

Plasma hormones and metabolites in Piedmontese cows during late pregnancy: relationships with calf birth weight

Relationships among plasma hormonal and metabolic variables in the last trimester of gestation in 59 Piedmontese dams (n = 15 heifers, n = 44 cows) and the calf birth weight (BWT) class of their offspring were investigated in seven herds. The BWT data were categorized as follows: > 50 kg (BWT-A), 46 to 50 kg (BWT-B), 41 to 45 kg (BWT-C), and < 41 kg (BWT-D). Blood samples were collected at 33, 36, and 39 wk of gestation. Packed cell volume (PCV) and plasma concentrations of insulin, estrone sulfate (E1SO4), NEFA, and creatinine were determined and correlated to BWT class. Creatinine: E1SO4 ratio also was calculated. Duration of gestation was greater for dams producing a BWT-A calf than for the other BWT classes, and calf BWT was heavier (P < 0.001) for calves in the BWT-A vs. BWT-D class. The heaviest calf in BWT-A was associated with the highest calving difficulty score. Insulin and PCV values were not affected by week of gestation, whereas plasma E1SO4, NEFA, and creatinine content increased (P < 0.001) and creatinine:E1SO4 decreased (P < 0.001) during late gestation. Calf BWT class did not affect PCV value. Plasma E1SO4 concentrations were lower (P < 0.01) in BWT-D dams than the other dams, showing the greatest difference at 39 wk of gestation. At 36 and 39 wk of gestation, dams bearing BWT-C and BWT-D calves had a higher (P < 0.01) plasma insulin concentration than those bearing BWT-A and BWT-B calves. Plasma NEFA concentrations at 39 wk of gestation were higher (P < 0.05) in dams of calf BWT-A than in the other dams. We conclude that plasma E1SO4 level is a variable that can be used to monitor problems related to a small size calf. Conversely, the forthcoming birth of a calf with a heavy BW seems to be preceded by a pronounced increase in plasma NEFA level in the dam just a few days before calving.     

Transfer of Beef Embryos in Dairy Cows: Influence of Recipient and Embryo Quality on Pregnancy Rate and Calving Performance

Contents
On three experimental farms 205 deep frozen Blonde d'Aquitaine embryos were transferred into Holstein dairy cows 7 days after a spontaneous heat. The aim of the study was firstly to examine the influence of recipient and embryo quality on pregnancy rate and secondly to study the calving performance of dairy cows carrying beef embryos. Recipients were divided into three groups based on the quality of the corpus luteum (unsuitable, moderately suitable and suitable) established by rectal palpation. Embryos classified as fair, good and excellent, were randomly distributed over the recipients, including those classified as being unsuitable. The overall pregnancy rate was 36% (standard deviation (SD) = 3.3), dystocia occurred in 48% of births (SD = 5.9), gestation was 297 days (SD = 1.2) and birth weight was 52 kg (SD = 2.0). No statistical differences were found in pregnancy rates and calving performance between the groups of recipients or between the classes of embryos. It is concluded that there is no justification to reject recipients on the basis of the quality of the corpus luteum. Furthermore there is no reason to reject fair embryos for transfer. Beef embryos in dairy cows resulted in much dystocia because of high birth weight, and in long gestation periods.     

不同全株玉米青贮饲喂量对妊娠期母牛体况、血液指标及后代犊牛的影响

试验旨在研究全株玉米青贮饲喂量及精粗饲料配比对妊娠期母牛体况、血液指标及后代犊牛的影响。选用40头体重相近、2岁、1胎的妊娠期7个月左右的西门塔尔母牛,随机分为4组,每组10头,试验期3个月。Ⅰ组每头每天饲喂全株玉米青贮14 kg、燕麦秸1 kg、精料补充料3 kg,Ⅱ组每头每天饲喂全株玉米青贮19 kg、燕麦秸1 kg、精料补充料1 kg,Ⅲ组每头每天饲喂全株玉米青贮19 kg、燕麦秸2 kg,Ⅳ组每头每天饲喂全株玉米青贮22 kg、燕麦秸1 kg。产犊后各组母牛统一更换为泌乳料,母牛带犊哺乳,6月龄断奶。结果表明:Ⅳ组的干物质摄入量低于Ⅰ组(P<0.05);Ⅲ组和Ⅳ组的氮摄入量低于其他组(P<0.01),Ⅰ组最高(P<0.01);Ⅲ组的纤维摄入量高于其他组(P<0.01);各组体况评分无差异;妊娠期7月末,Ⅳ组血液锰含量低于其他组(P<0.05);妊娠期9月末,Ⅲ组和Ⅳ组的血清尿素氮含量低于其他组(P<0.01);Ⅳ组母牛所产犊牛的胸围低于Ⅰ组和Ⅱ组(P<0.05),且有3头因生长缺陷被淘汰;6月龄时,各组犊牛体况指标无差异。综上,推荐肉牛能繁母牛妊娠后期每日提供全株玉米青贮19 kg、燕麦秸1~2 kg、精料补充料0~1 kg。     

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.