Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age

ABSTRACT Body development and reproductive performance of a hundred forty-two 14 to 15-month-old heifers, classified at weaning according to frame size as small, medium, and large, were evaluated. The parameters evaluated were: body weight, hip height, body condition score, weight gain, ovarian activity, and pregnancy rate. At weaning, body weight and hip height were significantly different among frame scores, (small – 133.0 kg, 92.2 cm; medium – 158.5 kg, 96.6 cm; and large – 185.2 kg; 100.2 cm). After weaning, heifers grazed together on natural pastures during the autumn and on ryegrass (Lolium multiflorum La.) during the winter and spring. Frame score differences remained until the beginning of the breeding season (BS), starting on average at 14 months of age. Weight gain between weaning and the beginning of BS was not different among frame scores (0.740 kg/day, on average). Body weights at the beginning of the BS were significantly different, of 255.7 kg (53.3% of the mature weight) for small heifers, 285.0 kg (59.4%) for medium heifers, and 307.6 kg (64.1%) for large heifers. Ovarian activity at the beginning of the BS was not different among the three groups. The average weight gain values during the BS of 0.492, 0.472, and 0.421 kg/day for small, medium, and large heifers, respectively, were significantly different. Pregnancy rates were not different among groups (small, 71.4%; medium, 76.4%; and large, 76.5%). Frame score did not influence the reproductive performance of heifers, but the small and medium heifers conceived 29 and 20 days earlier, respectively, than the large heifers

Assessment of bone metabolism in pregnant heifers with high and low residual feed intake

1 página. Póster presentado al Joint Annual Meeting (Phoenix, Arizona,Jul 15-19,2012)It is known that ruminants with lower residual feed intakes (RFI) use nutrients more efficiently than animals with higher RFI. However, the biological reasons and metabolic consequences underlying the variation in RFI between animals are not clear. There is also no information on whether RFI is related to differences in bone metabolism. Within this context 26 pregnant heifers (13 low RFI + 13 high RFI) in their first trimester of gestation were used for a bone metabolism study. Their blood was sampled once in the morning before feeding through jugular catheterization for analysis of osteocalcin and crosslaps in serum. These compounds are biochemical markers of bone formation and resorption respectively considered important clinical tools for assessment and monitoring of bone metabolism. Both markers were determined quantitatively using an immunoassay kit specifically for bovines. The results showed a lack of difference between animals with high and low RFI in the concentration of osteocalcin in serum with average concentration of 27 ± 10.9 ng/mL similar for both groups (P > 0.05), indicating that the efficiency of feed utilization by pregnant heifers does not affect their bone formation. Likewise the concentrations of bovine crosslaps were similar between the 2 groups of animals (P > 0.05), though the more efficient animals had a mean concentration of 16 ± 10.3 ng/mL and the group of animals with higher RFI gave a mean concentration of 8 ± 7.7 ng/mL. These findings suggest bone resorption is not affected by feed efficiency in pregnant heifers. Thus, this research provides an indication that bone metabolism is similar for pregnant heifers with lower and higher RFI. However more research is needed to provide further information.Peer reviewe

Meta-analysis of the effects of the interaction between copper and molybdenum on weight gain and gain: feed ratio in growing cattle

1 página.-- Trabajo presentado al Annual Joint Meeting of the American Dairy Science Association (ADSA) and American Society of Animal Science (ASAS), Nueva Orleans, Luisiana (USA). J. Anim. Sci. Vol. 89, E-Suppl. 1/J. Dairy Sci. Vol. 94, E-Suppl. 1: 616 (2011)Copper and molybdenum are essential trace minerals for proper functioning of many biological systems in ruminants. A variety of disease conditions are caused by lack of copper in the feed or by excesses of other minerals such as molybdenum which bind to copper and make it unavailable. Adequate trace mineral supply favors animal performance...Peer reviewe

Utilization of macrominerals and trace elements in pregnant heifers with distinct feed efficiencies

9 páginas, 5 tablas.The objective of the study was to evaluate utilization of dietary minerals and trace elements in pregnant heifers with distinct residual feed intakes (RFI). Feed intake, body weight (BW), and body composition traits were recorded in 36 crossbred heifers over a period of 37 wk, starting shortly after weaning at 8.3 (0.10; standard deviation) mo of age with an average BW of 276 (7.8) kg. Both BW and body composition were monitored regularly throughout the study, whereas individual feed intake was assessed during the last 84 d of the trial. Data recorded were used to calculate RFI for each heifer. Heifers were ranked based on RFI and assigned to high (n = 14) or low (n = 10) RFI groups. After the RFI study, 24 selected heifers [age 18.2 (0.14) mo; 87.5 (4.74) d in gestation; 497 (8.5) kg of BW] were used in an indirect digestibility trial (lignin as internal marker). Heifers were fed a ration containing corn silage, haylage, and a mineral premix in which Ca, P, K, Na, Mg, S, Cu, Fe, Mn, Mo, Se, Zn, and Co were provided in the diet according to National Research Council requirements of pregnant replacement heifers. The digestibility trial lasted 1 wk, during which samples of feces were gathered twice daily, and blood and liver biopsy samples were collected on the last day. We noted no significant differences between low- and high-RFI heifers in dry matter digestibility. Apparent absorption of Cu, Zn, and Mn was increased in heifers with low RFI, and apparent absorption of Co tended to be greater for these animals. Concentrations of macrominerals and trace elements in serum of pregnant heifers were similar for both groups except for Se, which was increased in the serum of low-RFI heifers. Liver concentrations of Cu, Fe, Mn, Mo, Se, and Zn did not differ between low- and high-RFI heifers. In conclusion, whereas improved absorption of some trace elements (Cu, Zn, Mn, and Co) and increased Se serum concentration appear to be associated with superior feed efficiency in pregnant heifers, further studies are needed to investigate the causality of such relationships.This project was funded in part through the Growing Forward Program (Agricultural Adaptation Council, Guelph, ON, Canada); the Beef Cattle Research Council (Canadian Cattleman Association, Calgary, AB, Canada); the Agriculture and Agri-food Canada (Ottawa, ON, Canada); the Beef Farmers of Ontario (Guelph, ON, Canada); the Ontario Ministry of Agriculture, Food and Rural Affairs (Guelph, ON, Canada); and the Canada Research Chairs Program of the Natural Sciences and Engineering Research Council of Canada (Ottawa, ON, Canada).Peer Reviewe

A meta-analysis of the effects of dietary copper, molybdenum, and sulfur on plasma and liver copper, weight gain, and feed conversion in growing-finishing cattle

12 páginas, 6 tablas.The minerals Cu, Mo, and S are essential for metabolic functions related to cattle health and performance. The interaction between Cu, Mo, and S can determine the utilization of each mineral, in particular Cu, by ruminants. A meta-analysis was performed to evaluate the effects of dietary Cu, Mo, and S and their interactions on plasma and liver Cu, ADG, and G:F in growing-finishing cattle. Data were collated from 12 published studies. The model with the best fit to data indicated plasma Cu was positively affected by dietary Cu (P 0.05). Average daily gain was negatively affected by dietary Mo (P 0.05). The interaction between S and Mo affected (P < 0.01) G:F, which was likely related to a positive response with the proper balance between these minerals. In conclusion, dietary Cu, Mo, and S and the Cu:Mo ratio caused changes in plasma Cu. Only dietary Mo and S led to a negative response in the performance of growing-finishing cattle, whereas the diet Cu:Mo ratio has a linear and quadratic effect on ADG. Nutritionists and producers need to consider with caution the supplementation of growing-finishing cattle diets with Mo and S because of their potentially adverse effects on animal performance. An appropriate Cu:Mo ratio is desirable to minimize the effects of an impaired supply of Mo on Cu metabolism and ADG. © 2013 American Society of Animal Science. All rights reserved.Peer Reviewe

Meta-analysis of the effects of dietary copper, zinc and iron on serum and liver copper and growth performance in growing-finishing cattle

2 páginas. Trabajo presentado al Proceedings of the canadian Society of Animal Science 60th Annual Meeting (Halifax, Nova Scotia, May 4-5, 2011).Peer Reviewe