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Nutrition plays a key role in the maintenance of animal reproductive performance. Reduced reproductive efficiency can decrease the profitability of dairy production by increasing days open, calving interval, the number of services per conception, culling rate, and veterinary services. Nutritional requirements increase rapidly with milk production after calving, but an improper diet plan could result in a negative energy balance (NEB). NEB delays the time of first ovulation through uncoupled hormones production. A diet high in fat could prevent the NEB state by increasing the energy status of animals. Protein supplementation supports high production but can also have severe effects on the reproductive performance of the animal. Deficiency of minerals can also alter the reproductive performance of the animal. This article has generally focused on the effects of various nutrients on reproductive efficiency of dairy cattle.
The study was aimed to determine an effect of various feed mixes on finishing White Improved billies reared until 6 months of age. The experiment was carried out in three replications. The study focused on the following sets of traits: body weight gain, feed consumption per weight gain, carcass and half-carcass measurements, slaughter performance and carcass tissue composition. The experiment has shown that farm-made balanced diets, which have a slightly lower level of protein but are richer in fibre, can be successfully used in feeding finishing White Improved billies. Namely, animals fed on this diet, although showing some performance parameters slightly reduced, achieved their slaughter value and meat quality similar to those fed on commercial CJ feed.
Because of the antimicrobial role that defensins play in humans and animals, genes encoding these peptides may be considered as molecular markers of a genetically determined susceptibility (or resistance) of the mammary gland to mastitis. Records were gathered of daily milk yield, fat, protein, and lactose content of milk, and milk somatic cell count (SCC) of 217 lactating Black-and-White cows. To determine the defensin gene polymorphism, DNA was isolated from blood and the RFLP method with enzyme TaqI was used. Twenty different polymorphic systems were revealed, possibly representing variants of genes encoding different defensins. Statistical evaluation included cows with more than seven records, and showing the 2.5% frequency of combined defensin genotypes (CDGs). In this way 13 different CDGs of 204 cows appeared available for statistical evaluation. CDGs significantly affected all dairy performance traits studied, as well as SCC. The important message from these results is that the defensin(s) may probably be used as genetic marker(s) in the breeding programmes aiming at selecting highly productive dairy cattle with increased resistance to udder infections.
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