中国荷斯坦牛部分乳房结构特性对泌乳性能的影响

本研究对规模化场奶牛乳房结构部分性状进行评价和测定,旨在分析其影响因素及其与泌乳性能的关系。现场评价和测定我国北方6个规模化奶牛场荷斯坦牛的乳房均衡(2 030条)、乳头长度(1 551条)和乳头位置评分(分前、后乳头,2 839条),使用SAS 9.2 GLM过程采用固定效应模型分析影响上述3个乳房性状的因素,同时分析3个单项性状对校正日产奶量和体细胞评分的影响。结果表明:场和胎次对3个乳房性状影响极显著(P0.01);前、后乳头位置和后乳头长度对校正日产奶量有显著影响(P0.05),校正日产奶量与前乳头位置评分值呈正比,与后乳头位置评分值呈反比;前乳头位置和长度对体细胞评分有显著影响(P0.05),体细胞评分随前乳头位置评分的增大而减小;5~5.5 cm的乳头长度对于校正日产奶量和体细胞评分都最佳。本研究结果为通过乳房性状选择、淘汰并提高奶牛的生产性能、乳房健康提供了参考。     

Mammary development and milk production in the sow: Effects of udder massage, genotype and feeding in late gestation

The primary aim of the study was to investigate whether post-ejection udder massage 1–2 weeks pp (post partum) had an effect on the amount of mammary tissue and milk production in the domestic sow.

The nursing behaviour of 35 primiparous LYL or YLY sows and their litters was followed on days 7 and 14 pp. The milk production was measured by the weigh–suckle–weigh method of the whole litter on days 11 and 18 pp. After weaning on day 28 pp, the sows were slaughtered and the mammary tissue excised and weighed.

No significant correlations were found between the duration of post-ejection udder massage and the subsequent milk production. LYL sows had more mammary tissue (P < 0.05) and their piglets spent more time performing post-ejection udder massage compared to the YLY sows (P < 0.01). Individual variation was found in the proportion of time that the sows were lying on either their right or left side. The weight of the mammary tissue from the left side was positively affected by the amount of udder massage (pre- and post-ejection massage) that the sows had received while lying on the right side relative to the amount that she had received while lying on the left side on day 7 pp (P < 0.01).

In conclusion, the intensity of udder massage influenced the amount of mammary tissue at slaughter. The genotype of the sow affected the expression of nursing behaviour and milk production. No connection was found between post-ejection udder massage and the measures of milk production 1–2 weeks pp. Finally, feeding during the last half of gestation affected the nursing behaviour.     

Interrelationships between herd management practices and udder health status using canonical correspondence analysis

The relationships between the herd-level distribution of udder health measures (traumatic, physical, functional and congestive udder disorders, clinical mastitis and somatic cell counts (SCC) greater than 400 × 10³, ml⁻¹) and farm (general hygiene, milking practices and housing system) and aggregated individual characteristics were studied by canonical correspondence analysis (CCA). This is a correspondence-analysis technique in which the axes representing disease patterns are expressed as linear combinations of potentially explanatory variables. These main axes can be drawn so that the distribution of diseases for combinations of the main-explanatory managerial variables can be visualized. The type of quarantine for newcomers, type of animal housing, presence of shelter at pasture, use of udder towel before milking, milk production and loss of body condition after calving, were strongly correlated with udder health status. Mastitis and physical udder disorders were associated with the combination of no introduction of replacement heifers and low loss of body condition after calving. Congestive disorders were more common on farms when no quarantine for newcomers was combined with high loss of body condition after calving. Higher clinical and subclinical mastitis incidence risks were associated with the combination of no udder towel, loose housing with high animal density and high milk production. In most cases, clinical mastitis and high SCC were explained by the same covariates but with contrasting levels of those covariates.     

Effect of restricted suckling on milk yield,milk composition and udder health in cows and behaviour and weight gain in calves,in dual-purpose cattle in the tropics

The study was conducted to evaluate the effects of restricted suckling (RS) in dual-purpose cows and calves compared to artificial rearing (AR). Twelve Holstein-Zebu cows with calves were assigned to each treatment. Cows were milked once daily in the morning with calves present to stimulate milk let-down. RS calves suckled 30 min after milking and 30 min in the afternoon, whereas AR calves were milk-fed from nipple bottles. The daily saleable milk yield was higher in RS than in AR cows (p < 0.01; 7.44 vs 6.50 kg/day), whereas RS cows had lower milk-fat content (p < 0.001). AR cows had higher California Mastitis Test scores (p < 0.001) and lower lactose content (p < 0.001) compared to RS cows, which indicates an improved udder health in RS cows. AR calves displayed more ‘cross-suck’ during suckling/milk feeding (p < 0.001) and during observations of general behaviour (p < 0.05), and more ‘lick and sniff interior’ during milking (p < 0.05) and suckling/milk feeding (p < 0.01), compared to RS calves. During observations of general behaviour the RS calves were more often observed to ‘walk’ (p < 0.01) and ‘lick self’ (p < 0.05) and less frequently to ‘eat concentrate’ (p < 0.05) than AR calves. Results support the hypothesis that RS increases milk yield, influences milk composition and improves udder health in cows, and decreases abnormal sucking in calves.     

Risk factors for udder edema and its association with lactation performance on primiparous Holstein cows in a large Florida herd, U.S.A

The objective of this study was to determine risk factors for udder edema (case–control study) and to evaluate the association of udder edema in primiparous Holstein cows with their lactation performance (cohort study). Values for the first 10 test day for milk yield, fat, protein, and somatic cell counts (SCC) linear score as well as mature equivalent (ME) 305 days milk yield, fat, protein, SCC linear score, and incidences of periparturient diseases from a computerized farm recording system were compared between primiparous cows with and without udder edema. Data consisted of 118 dairy heifers with udder edema, induced for parturition, and treated with diuretics and 889 control heifers that received no treatment. Primiparous cows giving birth to male calves, were 1.72 (1.01, 3.24; 95% CI) times more likely to develop udder edema than cows giving birth to female calves. Primiparous cows calving in winter season were 3.68 (1.09, 12.5; 95% CI) times more likely to develop udder edema than cows calving in summer. For each extra 10 cm in height the odds of udder edemas was 1.23 (1.03, 1.47; 95% CI). The first test day DHIA milk yield was lower in cows that developed udder edema (3.6 kg/day) than in normal cows. However, the subsequent test days and ME measurements were not statistically different between groups. Cows with udder edema were 1.62 (1.18, 2.14; 95% CI) times more likely to develop udder edema in the second lactation than control animals. It is concluded that the gender of the offspring, calving season and height at parturition were significant risk factors for udder edema. Only milk yield on the first DHIA test day was lower in cows with udder edema than in cows without udder edema.     

Mammary histology and alveolar cell differentiation during late gestation and early lactation in mammary tissue of beef and dairy heifers

Quantitative histology of mammary parenchymal tissue from 16 Hereford and 16 Holstein heifers was determined for tissue obtained on day 150, 180, and 280 of gestation and on day 49 of lactation. Percent area occupied by stromal tissue was progressively decreased on each consecutive sample day during gestation in Herefords and was lower in both breeds during lactation. Overall, area occupied by stromal tissue elements was also greater in Herefords. Percent lumenal space and number of cells per alveolar cross section was consistently greater for Holsteins and increased across sample periods in both breeds. During lactation more than 40% of the alveolar cells in Herefords were characterized as poorly differentiated, but in Holstein heifers nearly all of the cells were classified as either intermediate or fully differentiated. These data provide additional evidence to support the idea that much of the difference in milk production between beef and dairy animals depends on increased mammary function. Whether differences in milk production within dairy breeds are also explained by altered cellular differentiation remains to be determined.