Effects of selenium supplementation on plasma progesterone concentrations in pregnant heifers

It is known that selenium (Se) has various functions in animals. Many investigations on the biochemical and physiological effects of Se have been previously reported; however, the detailed function of Se in reproduction is not yet clear. We proposed the possibility that Se plays a notable role in progesterone production. The aim of this study was to clarify the effects of Se supplementation on progesterone levels of pregnant Holstein heifers. Eight Holstein heifers (?Se) were fed basal diet (containing 0.022 ppm of Se) throughout the experiment. While a 0.3 ppm diet of Se (sodium selenite) was fed to another seven animals (+Se) with basal diet. Blood sampling was carried out every week. Plasma Se concentrations were higher in Se‐supplemented cows compared with controls (?Se) (P < 0.01) throughout the experiment. Se supplementation increased plasma progesterone in the 29–39 weeks of pregnancy from 4.98 ± 0.64 to 6.86 ± 0.49 ng/mL on average (P < 0.05). The present findings suggest that Se contributes to maintaining the function of the corpus luteum and/or placenta in the latter period of pregnancy.     

Association of CXCR1 polymorphisms with apoptosis,necrosis and concentration of milk neutrophils in early lactating dairy heifers

Associations between polymorphisms in the candidate gene CXCR1, encoding the chemokine (C-X-C motif) receptor 1, and udder health have been identified before. In the present study, associations between the CXCR1 genotype (whole coding region) and apoptosis, necrosis, and concentration of milk polymorphonuclear neutrophilic leukocyte (PMNL) of 292 quarters belonging to 73 early lactating dairy heifers were studied. In uninfected quarters, % milk PMNL apoptosis was higher in c.980GG heifers [least squares means (LSM) 27%] compared to c.980AG heifers (LSM 16%), whereas in infected quarters, % milk PMNL apoptosis was higher in c.642GG heifers (LSM 29%) compared to c.642AG heifers (LSM 18%). Differences in milk PMNL concentration between infected and uninfected quarters were smaller in c.980AG heifers than in c.980GG heifers. An association between the CXCR1 genotype and necrosis of milk PMNL could not be demonstrated. Results indicate that CXCR1 polymorphisms influence viability and concentration of milk PMNL and provide a foundation for future research.     

Feeding dairy calves and replacement heifers in South-western Sweden: a survey

Daily feed rations, their nutrient contents and live weight gains were recorded for calves and replacement heifers from birth to calving in 122 Swedish dairy herds. Preweaned calves were fed whole milk (45% of the herds), milk replacer alone or milk replacer combined with whole milk. Calf starters were the most frequently used concentrates for preweaned calves, whereas grain dominated for weaned calves and heifers. Grain was supplemented with protein concentrates until 6 months of age and at calving. Grass/clover hay was the dominant forage for preweaned calves, whereas grass/clover silage alone or in combination with hay was the most common forage for calves and replacement heifers from 6 months of age. Heifers grazed semi-natural grasslands, leys or a combination of semi-natural grasslands and leys in 33, 15 and 52% of the herds, respectively. According to Swedish recommendations, calves in a majority of the herds were fed too low concentrations of crude protein from weaning to 6 months of age and calves were fed too low a metabolizable energy content inadequate for a daily weight gain of 700 g at weaning. Median live weight gain from birth to calving was only 567 g per day. Correct feed ration formulations and strategic grazing management could be means to increase weight gain and hence to decrease rearing costs of calves and replacement heifers in Swedish dairy herds.     

Feeding Strategies for Rearing Replacement Heifers in Small-scale Dairy Production Systems in the Highlands of Central Mexico

The growth of Holstein heifers in the campesino dairy systems in the highlands of Mexico was evaluated in three feeding strategies. Thirty-three heifers from 11 farmers, grouped according to strategy, were weighed every 14 days for 28 weeks. The live weight change over each 14-day period was estimated by individually regressing live weight over period, taking the regression coefficient as an unbiased estimate of live weight change. Regression coefficients were analysed as a randomized design with feeding strategies as treatments. Strategies were as follows: S1: grazed or cut pasture all year, maize silage and maize straw in the dry season, and 1.0–1.5 kg concentrate/heifer per day. S2: maize straw in the dry season, cut pasture forage, grazing of native grass, weeds from maize fields, and 1.0–1.5 kg concentrate/heifer per day. S3: maize straw in the dry season, grazed native grasses and weeds in the rainy season. Live weight gains were: S1, 0.511 kg/heifer per day; S2, 0.271 kg/heifer per day; and S3, 0.252 kg/heifer per day. Despite the better gains in S1, they are 24% below recommendations, arriving to service at 20 months of age. Not rearing their replacements may be a better alternative for campesino farmers under current economic conditions.     

西门塔尔牛、安格斯牛杂交生产利用研究

为了探讨西门塔尔牛和安格斯牛杂交改良本地黄牛效果,采用西门塔尔牛和安格斯牛作为肉牛终端父本,分别与本地黄牛开展二元经济杂交,对杂交F1体重变化、屠宰性能数据进行了统计分析研究。结果表明：两者杂交F1均比本地黄牛生长速度快且产肉率高,可有效提高本地黄牛的屠宰性能。说明西门塔尔牛和安格斯牛改良本地黄牛杂交优势明显,可有效增加本地黄牛养殖的经济效益,值得推广。     

Rumen fermentation pattern of dairy heifers fed restricted amounts of low, medium, and high concentrate diets without and with yeast culture

Restricted feeding and high concentrate diets are potential strategies for growing dairy heifers. Ruminal manipulation with additives such as Saccharomyces cerevisiae yeast culture (YC) has been shown to alter digestibility when added to this type of diet. An experiment was conducted to investigate the ruminal fermentation and in situ digestibility of diets with 3 different levels of forage to concentrate (F:C) fed at restricted intake without and with YC addition. Three cannulated post-pubertal Holstein heifers (age 18.0 ± 1.2 months; body weight 449.6 ± 19.7 kg) were fed diets consisting of corn silage as the sole forage source in a 3 period (35-day) Latin square design. Heifers were fed diets for 21 days with no YC addition, followed by 14 days where YC was added to the diet (1 g/kg as fed basis). Low (LC), medium (MC), and high (HC) concentrate diets (20, 40, and 60% concentrate) were fed once daily on a restricted basis to provide 0.22 Mcal ME/kg empty BW^0.75. Rumen fluid was sampled on days 18 and 32 of each period, and rumen contents were evacuated on days 21 and 35 of each period. An in situ study was done on days 14 to 17 and on days 28 to 31. Mean ruminal pH was not different between dietary treatments and no YC effect was detected. Mean total volatile fatty acids (VFA) and ruminal ammonia-nitrogen (NH₃-N) concentration was also not different among diets with different F:C. Molar proportions of acetate were decreased, and propionate were increased; while the acetate-to-propionate ratio was decreased as the concentrate level increased from LC to HC. Total VFA, propionate, and acetate as well as isoacids concentration increased, yet NH₃-N concentration decreased with YC addition in all diets. From these results we conclude that feeding HC diets in restricted amounts had minimal effects on rumen fermentation rate between different F:C diets. The addition of YC modified NH₃-N and volatile fatty acid concentrations in the rumen in all 3 diets in this study, presumably through alterations in end-product production and utilization.     

西黄杂种公牛与牦牛杂交试验研究报告

对牦牛三元杂交又一个组合(西×黄)♂×牦牛♀的研究结果表明,含1/2西门塔尔牛血缘的西黄杂种公牛从 半农半牧区引进川西北高寒牧区有良好的适应性,与牦牛自然交配,繁殖成活率达43.85％,比用"冻配"技术生产犏牛 提高20.15个百分点。繁殖的F1代犏牛杂种优势明显,初生重大,公、母分别为(21.74±2.49)kg、(20.83±3.62)kg,相 应比牦牛高8.24 kg和7.58 kg(p<0.01);生长发育快,2.5岁时,公、母体重分别为(326.75±13.61)kg、(321.29±13.35)kg, 比同龄牦牛相应重142.45 kg和165.43 kg(p<0.01),杂种优势率高达40.42％;母犏牛2~3岁可初配,比母牦牛提前1-2岁 投入生产,第一胎挤奶量(704.55±30.69)kg,为同胎次母牦牛的2.83倍(p<0.01)。建议在牦牛改良中推广(西×黄) ♂×牦牛♀和(黑×黄)♂×牦牛♀两个牦牛三元杂交组合。     

Effects of dietary n‐6/n‐3 fatty acid ratio on nutrient digestibility and blood metabolites of Hanwoo heifers

The objectives of this study were to investigate the effects of dietary n‐6/n‐3 fatty acid (FA) ratio on digestibility, blood metabolites and FA profile of Hanwoo heifers. Fifteen Hanwoo heifers (22 ± 3 months old; 357 ± 69.7 kg) were randomly assigned to three dietary treatments with n‐6/n‐3 FA ratios of 2.07, 5.18 and 7.37. The animals were housed individually in digestion crates and fed total mixed rations at 2.2% of body weight for 2 weeks of adaptation and 1 week of collection. Treatment effects on in vivo digestibility, plasma metabolite and fatty acid profiles, and in vitro ruminal fermentation and fatty acid profiles were examined. In vivo digestibility was not affected (P > 0.05) by dietary n‐6/n‐3 FA ratio. However, in vitro dry matter digestibility and concentrations of total volatile fatty acids and propionate decreased (P < 0.05) linearly with increasing n‐6/n‐3 FA ratio. Plasma insulin and progesterone increased linearly (P < 0.05), but linolenic acid and total n‐3 FA decreased linearly (P < 0.05) with increasing n‐6/n‐3 ratio. Increasing the dietary n‐6/n‐3 FA ratio can increase the n‐6/n‐3 FA ratio in plasma and ruminal fluid as well as plasma progesterone secretion.