Browsing IJAFR, volume 44, 2005 by Publication date
Now showing items 21-23 of 23
Effects of supplementary concentrate level with grass silage, and separate or total mixed ration feeding, on performance and carcass traits of finishing steers(Teagasc (Agriculture and Food Development Authority), Ireland, 2005)Concentrates are a major component of feed costs in winter finishing of beef cattle. The objectives of this study were (1) to determine the response to increasing levels of supplementary concentrates with grass silage, and (2) to determine the effects of feeding silage and concentrates separately or as a total mixed ration (TMR). A total of 117 finishing steers (mean initial live weight 538 (s.d. 35.5) kg) were assigned to a pre-experimental slaughter group of 9 animals and to 6 feeding treatments of 18 animals each. The feeding treatments were (1) silage only offered ad libitum (SO), (2) SO plus a low level of concentrates offered separately (LS), (3) SO plus a low level of concentrates offered as a TMR (LM), (4) SO plus a medium level of concentrates offered separately (MS), (5) SO plus a medium level of concentrates offered as a TMR (MM), and (6) concentrates ad libitum plus a restricted silage allowance (AL). Low and medium concentrate target levels were 3 and 6 kg dry matter (DM) per head daily. When silage (210g/kg DM, 758 g/kg in vitro DM digestibility, pH 3.7) and concentrates were fed separately, the daily concentrate allowance was given in one morning feed. The animals were individually fed for a mean period of 132 days. After slaughter, carcasses were weighed and graded and a rib (6th to 10th) joint was dissected into its component tissues. Silage DM intake decreased (P < 0.001) but total DM intake increased (P < 0.001) with increasing concentrate level. Average live-weight gains for SO, LS, LM, MS, MM and AL was 0.34, 0.86, 0.86, 1.02, 1.00 and 1.12 (s.e. 0.064) kg/day, respectively. Corresponding carcass weight gains were 0.25, 0.58, 0.58, 0.71, 0.68 and 0.82 (s.e. 0.028)kg/day. All measures of fatness increased (P < 0.05), bone proportion of the rib joint decreased (P < 0.001), and muscle proportion was not significantly affected by dietary concentrate level. There were no significant interactions between concentrate level and method of feeding. Compared with offering the feeds separately, feeding as a TMR increased silage DM intake by proportionately 0.06 (P < 0.05) and total DM intake by proportionately 0.04 (P < 0.05). Method of feeding had no significant effect on performance, slaughter or carcass traits. It is concluded that silage intake decreased and total intake increased with increasing concentrate level. Live-weight and carcass-weight gains also increased with increasing concentrate level. Feeding a TMR had no effect on animal performance or carcass traits compared with separate feeding.
Empirical algebraic modelling of lactation curves using Irish data(Teagasc (Agriculture and Food Development Authority), Ireland, 2005)The purpose of this study was to find a well-fitting, robust, single-equation model to describe the shape of lactation curves for Irish dairy cows. The suitability of a number of algebraic models that depict lactation curves was examined, using Irish test day data. The analysis was carried out on a total of 14,956 lactation records from commercial and experimental herds and included both autumn and spring calving animals. ‘Goodness of fit’ and adherence of the various models to the assumptions of regression analysis were examined. Multicollinearity posed a severe problem in the application of the best-fit model but omitting one of the variables from the estimation procedure reduced this effect. The modified model, referred to as the Ali-B model, is a single equation model that can be easily updated and incorporated into computer code. This is in contrast with the Standard Lactation Curve (SLAC) method, a method of interpolation, which is currently used by the Irish industry. The effects of seasonal factors on milk production were estimated and added to the Ali-B model to create a production profile for cows calving in specific months. The Ali-B model provided an acceptable level of accuracy in representing the shape of the lactation curve for Irish dairy cows, and can be easily modified for different environmental scenarios.
Post-weaning performance and carcass characteristics of steer progency from different suckler cow breed types(Teagasc (Agriculture and Food Development Authority), Ireland, 2005-04)In two experiments a total of 44 steer progeny of spring-calving Charolais (C) and Hereford × Friesian (HF) suckler cows and C sires were slaughtered at approximately 2 years of age. Following weaning they were offered silage and 1 kg of concentrate per head daily during a 5 month winter after which they spent 7 months at pasture. In Experiment 1, animals were given a silage/concentrate diet during a finishing period of either 95 or 152 days. In Experiment 2, steers were offered either a daily diet of silage plus 6 kg of concentrates or concentrates to appetite plus 5 kg of silage (fresh weight) during the final 140-day finishing period. Following slaughter, an 8-rib pistola from each animal was dissected. For the two experiments combined C and HF progeny had carcass weights of 372 and 385 (s.e. 6.1) kg, proportions of carcass as pistola of 467 and 454 (s.e. 2.8) g/kg and pistola meat proportions of 676 and 642 (s.e. 5.1) g/kg, respectively. All fat traits were lower for the C than HF progeny but there was no difference in carcass conformation score. Increasing slaughter weight increased carcass weight (P < 0.001), kidney plus channel fat weight (P < 0.001), and pistola fat proportion (P < 0.001) and decreased the proportions of carcass as pistola (P < 0.05), pistola meat (P < 0.01), and bone (P < 0.05). In conclusion, breed type had no effect on carcass growth but the C progeny had higher meat yield than the HF. Increasing slaughter weight increased fatness and reduced meat yield.