• The effect of supplementary grass silage and standard concentrate on milk fat fatty acid composition and iodine value when cows are fed a whole rapeseed-based concentrate at pasture

      Magowan, Elizabeth; Fearon, A.M.; Patterson, D.C. (Teagasc, Oak Park, Carlow, Ireland, 2010)
      The use of grass silage and concentrates to supplement fresh grass intake is commonly practised in dairy systems. However, the effects of such supplementation within a dietary regime designed to produce a spreadable butter are unknown. Sixteen Holstein Friesian cows were used in an incomplete changeover design to investigate the effect on milk fat of supplementation with grass silage (GS) or standard concentrate (SC) when offering a concentrate based on whole rapeseed at pasture (RC+G). A control diet of fresh grass and standard concentrate (SC+G) was also included. Diet had no effect (P > 0.05) on milk yield or on the lactose concentration of milk. The iodine value (IV; grams of iodine per 100 g milk fat) of milk fat with the RC+G diet was greater (43.9, P < 0.05) than with the SC+G diet (39.9). The iodine value of milk fat was reduced (P < 0.05) when RC+G+GS was offered (41.5 g/100g), but not when RC+G+SC was offered (43.1 g/100g), compared with when RC+G was offered. The proportion of unsaturated fatty acids in milk fat was higher (P < 0.05) when the RC+G diet was offered compared with either RC+G+GS or RC+G+SC. If supplementary feedstuffs are to be used in combination with a wholerapeseed- based concentrate and pasture, then inclusion of standard concentrate would be preferred over grass silage because the negative impact on the iodine value of milk fat was less. However, further research is required to investigate the effect on IV of milk fat when a standard concentrate supplement is offered at levels that increase milk yield.
    • Effects of finishing strategy on performance of Belgian Blue × Friesian and Limousin × Friesian steers.

      Keane, Michael G. (Teagasc, Oak Park, Carlow, Ireland, 2010)
      Belgian Blue and Limousin bulls are used for cross-breeding with Holstein Friesian dairy cows in Ireland. In beef winter-finishing enterprises, a preliminary feeding period sometimes precedes the finishing period. The optimum feeding level for this period has not been established. The objective of this study was to compare lifetime performance of Belgian Blue × Holstein Friesian (BB) and Limousin × Holstein Friesian (LM) steers and to determine the effects of three finishing strategies on performance and carcass traits. Fortyeight spring-born male calves (24 BB and 24 LM), the progeny of Limousin and Belgian Blue bulls out of Holstein Friesian cows, were reared together to slaughter. At about 19 months of age they were assigned to one of three finishing strategies involving grass silage ad libitum plus 0, 3 or 6 kg concentrates per head daily for 112 days (preliminary period) followed by concentrates ad libitum to slaughter at 610 kg live weight. Slaughter weight and carcass weight did not differ between the breed types but BB had a higher kill-out proportion, better carcass conformation and lower carcass fatness. Live-weight gains during the preliminary period were 431, 914 and 1134 g/day (s.e. 31.8; P < 0.001) for the 0, 3 and 6 kg/day concentrate levels, respectively. Overall gains for the combined preliminary and finishing periods for the treatments in the same order were 945, 1101 and 1081 g/day (s.e. 36.1; P < 0.01). There were few differences between the finishing treatments in slaughter weight, carcass weight or carcass traits. It is concluded that general productivity is similar for BB and LM but BB have superior carcass traits. Where a preliminary feeding period precedes a finishing period on ad libitum concentrates, animals fed a low level of supplementary concentrates require less feed energy to reach a fixed slaughter weight than those fed none or a higher level of supplementary concentrates.