RESUMEN
As the dairy industry continues to grow, more dairy calves are available for dairy, beef, and veal purposes. Rearing systems must be highly efficient to make this industry cost efficient, making the evaluation of rearing methods important to establish the most practical method. A study was designed and conducted to evaluate effects of housing and feeding systems on performance of neonatal Holstein bull calves. Treatments (2 × 2 factorial arrangement) consisted of: 1) individually housed, bottle-fed (n = 5 bull calves); 2) individually housed, bucket-fed (n = 5 bull calves); 3) group-housed, bottle-fed (n = 5 pens; 4 bull calves/pen); and 4) group-housed, bucket- (trough) fed (n = 5 pens; 3 or 4 bull calves/pen). Feeding treatments began on d 7 when calves had been acclimated to their new environment. Body weight measurements were collected every 7 d and blood samples were collected on d 0, 28, 55, and 66 for ß-hydroxybutyrate (BHBA) concentration as a gross indicator of ruminal development. No housing × feeding interactions or feeding treatment effects were observed (P > 0.10). Average DMI (dry feed plus milk replacer) was increased (P < 0.05) for group-housed vs. individual animals after d 41, and final BW was greater (P < 0.05) for group-housed calves compared with individually housed calves. Feed efficiency and ADG, however, remained similar (P > 0.10) for all treatments. Fecal scores (P > 0.26), CV for BW (P > 0.26), and BHBA concentrations (P > 0.14) showed no differences among treatments. Housing system had greater effect on calf performance compared with milk feeding regimen.
Asunto(s)
Crianza de Animales Domésticos , Animales Recién Nacidos , Bovinos/crecimiento & desarrollo , Vivienda para Animales , Envejecimiento , Alimentación Animal , Fenómenos Fisiológicos Nutricionales de los Animales , Bienestar del Animal , Animales , Industria Lechera , Dieta/veterinaria , MasculinoRESUMEN
The objectives were to determine if strategic supplementation of range cows with a long-acting (6 mo), trace mineral, reticulorumen bolus containing Cu, Se, and Co would: (1) increase cow BCS and BW, and calf birth, weaning, and postweaning weights, or weight per day of age (WDA); (2) increase liver concentrations of Cu or Zn in cows, or blood Se, Cu, or Zn concentrations in cows and calves; and (3) vary by cow breed for any of these response variables. There were 192 control and 144 bolused Composite cows (C; 25% Hereford, Angus, Gelbevieh, and Senepol or Barzona); 236 control and 158 bolused Hereford (H) cows; and 208 control and 149 bolused Brahman cross (B) cows used in a 3-yr experiment. Cows were weighed and scored for body condition in January, May, and September, and all bolused cows received boluses in January. Each year, from among the 3 breed groups a subset of 15 control and 15 bolused cows (n = 90) had samples obtained in January and May for liver Cu and Zn, blood Se, and serum Cu and Zn. As for cows, blood and serum from the calves of these cows were sampled each year in May and September for Cu, Se, and Zn. There was a significant breed x year x treatment interaction (P = 0.001) for cow weight loss from January to May. Calf WDA, weaning, and postweaning weights did not differ (P > 0.40) between bolused and control cows, but there was a significant (P = 0.022) breed x year x treatment interaction for birth weight. Liver Cu was deficient (< 75 ppm; P < 0.001) in control cows and adequate (< 75 to 90 ppm) for bolused cows. Liver Cu differed by year (P < 0.001). Blood Se was adequate (< 0.1 ppm) for all cows except in January 2001 and 2002. There was no difference (P > 0.50) in blood Se between treatment groups in January, but bolused cows had greater (P < 0.01) blood Se in May. Breed differences for blood Se concentrations existed for bolused cows, with B having greater (P < 0.05) blood Se than either C or H cows. Breed differences also existed for control cows, with H having less blood Se (P < 0.04) than B or C cows. Calves from bolused cows had greater blood Se than calves from control cows (P = 0.01). Supplementation via a long-acting trace mineral bolus was successful in increasing liver Cu in cows and blood Se in cows and calves, but the responses varied by year. Bolus administration had variable effects on BW change in early lactation, depending on breed and year, which may indicate the need for breed- and year-specific supplementation programs.
Asunto(s)
Crianza de Animales Domésticos , Bovinos/fisiología , Oligoelementos/administración & dosificación , Animales , Peso Corporal , Química Farmacéutica , Cobre/análisis , Cobre/metabolismo , Femenino , Hígado/química , Hígado/metabolismo , Selenio/sangre , Factores de Tiempo , Zinc/análisis , Zinc/metabolismoRESUMEN
The first wave of follicular development following ovulation in cattle is characterized by selection and growth of a large, estrogenic dominant follicle. After the follicle becomes morphologically dominant, concentrations of estradiol in its follicular fluid decrease abruptly. The purpose of this study was to determine whether this decrease in estrogen production is caused by an insufficient supply of androgen from theca interna or decreased aromatization of androgen precursor by granulosa cells. Dominant follicles were collected from Holstein heifers on d 4, 6, or 8 of the first follicular wave (n = 5/d). Amounts of 17alpha-hydroxylase mRNA in theca interna were sevenfold higher (P < 0.01) on d 4 than on d 8. After 3 h in culture, secretion of androstenedione by theca interna collected on d 4 (236 +/- 44 pg/microg of protein) tended to be lower (P = 0.055) compared with d 6 (517 +/- 162 pg/microg protein) and was lower (P < 0.05) compared with d 8 (387 +/- 51 pg/microg of protein). In granulosa cells, amounts of aromatase mRNA decreased (P < 0.05) on d 8 compared with d 6 but not d 4. In vitro secretion of estradiol was higher in granulosa cells collected on d 4 (3.5 +/- 0.8 ng/[10(5) cells x 3 h]) compared with d 6 (1.8 +/- 0.6 ng/[10(5) cells x 3 h]; P < 0.05) and tended to be higher on d 4 than on d 8 (2.2 +/- 0.2 ng/[10(5) cells x 3 h]; P = 0.058). We conclude that the decrease in estradiol production observed during atresia of the dominant follicle is not due to lack of androgen substrate for aromatization or downregulated expression of the aromatase gene, but may be the direct result of decreased activity of the aromatase enzyme within granulosa cells.