Effects of ensiled forage legumes on performance of twin-bearing ewes and their progeny

Abstract

Twenty-four twin-bearing mature Mule ewes were used to evaluate the effects of feeding ensiled red clover (Trifolium pratense), lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne) during late pregnancy on subsequent ewe and lamb performance. Eight weeks prior to lambing the ewes were individually penned and offered one of the treatment forages ad libitum (no. = 8 per silage). All ewes were supplemented with molassed sugar-beet shreds to avoid dietary energy being a limiting factor and to ensure the responses were primarily attributable to the forage protein content. Individual intakes of the ewes were determined daily and weekly measurements of ewe live weight and body condition score were made. The ewes were also scanned weekly for depths of subcutaneous fat and longissimus dorsi (LD) muscle. Blood samples were taken at 6, 4, 2, and 1 week(s) before lambing, 24 h after lambing and at 3 weeks after lambing and were analysed for serum concentrations of total protein (TP), albumin, urea, beta-hydroxybutyrate (BHB) and plasma concentrations of glucose and non-esterified fatty acid (NEFA). After lambing all ewes and their lambs were turned out to graze together on a ryegrass sward. The lambs were weighed at birth and at weekly intervals thereafter until 12 weeks post partum. The lucerne silage offered had a higher dry matter (DM) content than the red clover and ryegrass silages (367, 305 and 314 g DM per kg fresh matter, respectively;P< 0·001). Forage type significantly affected crude protein (CP) concentration (240, 215 and 182 g CP per kg DM for lucerne, red clover and ryegrass silages, respectively) and metabolizable energy (ME) density (11·1, 11·6 and 10·8 MJ ME per kg DM respectively). Ewes offered the legume silages had higher intakes of DM, CP and ME than ewes offered ryegrass silage (P< 0·05), which was reflected in higher ewe live-weight gain (P< 0·05) but not in litter birth weight (P> 0·05). Silage treatment affected serum concentrations of TP, albumin, globulins and urea during the last 4 weeks of pregnancy (P< 0·05). Lambs born from ewes offered lucerne and red clover silages prior to lambing had higher growth rates from birth to 3 weeks of age than those from ewes offered ryegrass silage (320, 323 and 282 g/day, respectively;P< 0·05). Lamb live weight at 12 weeks of age was higher for lambs from ewes that had been offered the red clover silage, at 29·1 kg compared with 26·7 and 27·1 kg for lambs from ewes previously offered lucerne and ryegrass silages (P< 0·05). In conclusion, the results showed that red clover and lucerne silages are better able to meet nutrient requirements of ewes in late pregnancy than grass silage.