Association between seasonal changes in fatty-acid composition, expression of VLDL receptor and bovine sperm quality.

Reduced reproductive performance of dairy cows during the summer is often associated with elevated temperature. Semen collected and cryopreserved during the summer may be of low quality and might contribute to the compromised fertility of dairy cows during this season. The present study examined the association between seasonality, semen quality and its potential to survive cryopreservation.

Summer heat stress alters the mRNA expression of selective-uptake and endocytotic receptors in bovine ovarian cells.

Summer heat stress (HS) is a major factor in decreased reproductive performance in high-producing dairy cattle, possibly by affecting the steroidogenic capacity of ovarian follicles and ovarian follicular dynamics. In the present study, mRNA expression of cholesterol receptors was determined in bovine ovarian cells. Two endocytotic receptors (very-low-density lipoprotein receptor (VLDLr) and low-density lipoprotein receptor (LDLr)), and two selective-uptake receptors (scavenger receptor class B type 1 receptor (SRB1) and the lipoprotein-receptor-related protein 8 (LRP8)) were evaluated.

Temporal folate status during lactation in mares and growth in foals.

Objective: To identify changes in folate status of mares and foals during lactation and growth, respectively.

Animals: 20 Thoroughbred mares and foals.

Procedures: Pregnant mares, and following foaling the same mares with their foals, were maintained on mixed grass-legume pasture and fed either a traditional dietary supplement rich in sugar and starch (SS) or a dietary supplement high in fat and fiber (FF).

Impaired immune responses in broiler hatchling hindgut following delayed access to feed.

One of the key stimulators of intestinal development in the chick is physical exposure to feed, while feed withholding delays the onset of gut development. A delay of 24-72 h in onset of feeding is quite common in the poultry industry due to variation in hatching time and hatchery treatments. As intestinal development occurs in concert with the development of the gut associated lymphoid tissue (GALT), we investigated the effects of short term feed withholding on development of GALT in broiler hatchlings.

Direct determination of optimal amino acid intake for maintenance and growth in broilers.

This study has used a direct approach to calculate the optimal dietary supply of amino acids for maintenance and growth in broiler chicks. Amino acid intake and accretion in the carcass in Ross 308 chicks was measured following the feeding of different experimental diets with controlled feed intake from hatching through 42 d. Increasing crude protein levels at constant amino acid:protein ratio improved growth and reducing the crude protein levels at constant amino acid:protein ratios depressed performance.