Complete diets for dairy cows: the effect of energy concentration and change in energy concentration of a complete diet on intake and performance of lactating dairy cows

Abstract

Ninety-two British Friesians (56 cows and 36 heifers) were divided into two groups during weeks 3-10 of lactation and received ad libitum either complete diet H (65 % concentrates, 35% grass silage, 11-7 MJ ME/kg D.M.) or diet M (50% concentrates, 50% grass silage, 11-2 MJ ME/kg D.M.). In weeks 11-20 half the animals of each group continued to receive the same diet (HH or MM) while the other half were changed from diet H to M (HM) or from diet M to L (ML). Diet L contained 35 % concentrates, 65% grass silage and 10-7 MJ ME/kg D.M. The crude protein concentration of all diets was maintained at about 157 g/kg D.M. by the addition of soya-bean meal to diets M and L.During weeks 3-10 the mean D.M. intake (kg/day), milk yield (kg/day), milk protein (g/kg) and live-weight change (kg/day) for animals on diets H and M were 15-0, 21-7, 33-3, 0-50 and 12-9, 20-2, 31-5, 0-35 respectively. Differences were significant for D.M. intake, milk yield and milk protein concentration. Although milk-fat concentration of cows given diet H (40-2 g/kg) was similar to that of cows given diet M (39-9 g/kg), heifers receiving diet H had a significantly lower value (37-0 g/kg) than those given diet M (39-8 g/kg).When animals were changed from diet H to M or from M to L at week 11, D.M. intake, milk yield and milk-protein concentration decreased. However, milk-fat concentration and live-weight change were generally unaffected.During the complete experimental period, weeks 3-20, animals on treatments HH, HM, MM and ML had mean D.M. intakes and milk yields of 15-3, 14-2, 13-2, 12-4 kg/day and 19-7, 18-5, 17-8, 17-0 kg/day. Milk-protein concentration, was closely related to D.M. intake, but only with heifers did diet H significantly depress milk-fat concentration. The highest live-weight gain was recorded on treatment HH (0-40 kg/day) and the lowost on treatment ML (0-29 kg/day) with intermediate values for treatments HM and MM.In vivo digestibility coefficients of D.M. and organic matter for diet H (0-731, 0-757) were significantly higher than those of diet L (0-707, 0-734) with intermediate values for diet M. However, for acid-detergent fibre the digestibility coefficient for diet H was significantly lower (0-562) than for diet L (0-662). The digestibility coefficients for nitrogen in all three diets were similar.Estimates of mean efficiency of utilization of ME for lactation were made on a weekly basis and were 0-56 and 0-64 for animals on diets H and M in weeks 3-10. During weeks 11-20 the mean values for animals on treatments HH, HM, MM and ML were 0-46, 0-53, 0-51 and 0-59, respectively.

Effect of feeding method on nutrient utilization and cow performance in limit-fed cow-calf systems

“…Proportions of propionate for all treatments numerically increased when the concentrate was delivered 2 h after concentrate was delivered. Similar to our results, Phipps et al (1984) reported no differences in proportions of acetate, propionate or butyrate when ingredients were combined or separated at restricted intake levels for dairy cattle. Also in agreement with our results, Yan et al (1998) found no differences in proportions of VFA or total VFA concentration when cows were fed a complete diet or separately fed the ingredients of that diet.…”

“…In cows fed ad libitum, DM digestion of a complete diet was reduced compared to cows fed the same ingredients separately ( Gordon et al, 1995 ). Improved DM and OM digestibility were also observed in cows fed separate ingredients compared to a TMR when intake was limited to 2.5% BW ( Phipps et al, 1984 ), although that degree of restriction is likely close to ad libitum feeding. The relatively higher feeding rates in these studies compared to the present study allowed some selectivity among separately fed ingredients, which resulted in improved digestibility when cattle were allowed separate access to ingredients.…”