The effect of level of nutrition prior to mating on the reproductive performance of ewes of two welsh breeds in different levels of body condition

Abstract

The effects of high-low (HL) and low-high (LH) patterns of nutrition during the 5 weeks prior to a synchronized mating were studied on the reproductive performance of 115 Welsh Mountain and 114 Brecknock Cheviot ewes in a range of body condition at the start of treatment. For 2 months prior to treatment imposition, ewes were grazed in a systematic way at different stocking rates on different sward heights to obtain a range of body condition scores. Target score groupings were 2·00 to 2·25, 2·50 to 2·75 and 3·00 to 3·25 and although scores of 1·50 to 3·25 were obtained, most lay in the 2·00 to 2·75 range. Two treatment groups, balanced for live weight and body condition score, received high and low levels of nutrition for 16 days from mid October, achieved, respectively, by a low stocking rate on a sward with a high surface height plus ad libitum concentrate and a high stocking rate on a sward with a low surface height plus 200 g hay per head per day. Treatments were then reversed for the 17 days prior to mating. Live-weight and body condition-score changes were recorded and reproductive performance at first mating was measured from counts of corpora lutea and viable embryos at slaughter either at return to service or at 4 weeks after first mating. There were no differences due to nutritional pattern in live weight or body condition score at mating. The LH treatment significantly increased the rates of ovulation, conception, multiple ova survival and potential lambing per ewe pregnant and per ewe mated in the Welsh Mountain breed but significantly increased only the rates of ovulation and potential lambing per ewe pregnant in the Brecknock Cheviot breed compared with the HL treatment. The relatively poorer response in the latter breed was partially due to a lower ovulation rate potential coupled with non-significantly lower rates of conception and survival of single-shed ova associated with the LH treatment. Much of this relatively poorer reproductive performance in the Brecknock Cheviot breed was in ewes with body condition scores 3= 2·75. Reproductive performance increased with increasing body condition at the start of treatment over the range of scores =≤ 2·25 to 2·50 in both breeds and, while continuing to improve in scores above 2·50 in the Welsh Mountain breed, in the Brecknock Cheviot breed it started to decline. Ewes with a body condition score of 2·50 in both breeds showed the greatest response in potential lambing rate to the LH treatment.

Efeito da sobrealimentação com fontes de proteína de diferentes degradabilidades sobre a ovulação em ovelhas Santa Inês

“…Durante a semana da ovulação, as ovelhas que receberam sobrealimentação com farelo de soja ou com glúten de milho e farelo de algodão apresentaram ECC de 2,75 ± 0,05 ou 2,85 ± 0,05, respectivamente. Segundo Gunn et al (1991), a condição corporal mínima para ovelhas lanadas de origem escocesa manifestarem sua capacidade reprodutiva é de 2,5. Assim, provavelmente, este pode ter sido o motivo da ausência de diferença no número de ovulações e da ausência de correlação entre o número de ovulações e o ECC, o peso vivo, o ganho de ECC e de peso vivo.…”

“…A ausência de diferença no número de ovulações foi atribuída ao fornecimento de um volumoso rico em proteína degradável no rúmen, que aumentou a quantidade de proteína degradável no rúmen na dieta total consumida. Além disso, as ovelhas já iniciaram o experimento com ECC de 2,57, acima do limiar de 2,5 estabelecido por Gunn et al (1991). No presente estudo, as ovelhas consumiram como volumoso a silagem de milho, que também é rica em proteína degradável no rúmen e nitrogênio não-proteico.…”

Supplementation with protected fat to manage gastro-intestinal nematode infections in Santa Ines sheep

“…More practical and accurate direct assessments of the nutritional status of a flock have been performed in several works (GUNN et al, 1991). The fact that many of the sheep lambed during the experiment is also noteworthy, as the variation in mean weight among the animals could be due to their physiological status.…”

“…Many studies on the interaction between protein and infections with ovine nematodes have been conducted (STEEL, 2003;LOUVANDINI et al, 2006); however, studies of the influence of dietary energy on the control of worms, particularly in tropical conditions, are necessary (HOSTE et al, 2005).…”

Efeitos da nutrição na atividade cíclica reprodutiva e nas concentrações plasmáticas de melatonina em ovelhas mantidas em pastagem e submetidas ao efeito macho durante o anestro sazonal.

“…O impacto da nutrição na atividade reprodutiva é causada por efeitos diretos e indiretos nos tecidos reprodutivos. Em ovelhas, a técnica conhecida como "flushing" (maior fornecimento de energia na dieta de duas a três semanas antes e durante a estação de monta) tem como objetivo aumentar a taxa de ovulação e melhorar a fertilidade (GUNN et al, 1991;KOTT, 2001;NEARY, 2001). Porém, os mecanismos exatos de como a nutrição afeta a reprodução não está bem esclarecido.…”