Influence of body condition at calving and postpartum nutrition on endocrine function and reproductive performance of primiparous beef cows1,2

Abstract

The influences of body condition score (BCS) at calving and postpartum nutrition on endocrine and ovarian functions, and reproductive performance, were determined by randomly allocating thin (mean BCS = 4.4 +/- 0.1) or moderate condition (mean BCS = 5.1 +/- 0.1) Angus x Hereford primiparous cows to receive one of two nutritional treatments after calving. Cows were fed to gain either 0.45 kg/d (M, n = 17) or 0.90 kg/d (H, n = 17) for the first 71 +/- 3 d postpartum. All cows were then fed the M diet until 21 d after the first estrus. A replication (yr 2; M, n = 25; H, n = 23) was also used to evaluate reproductive characteristics. Concentrations of IGF-I, leptin, insulin, glucose, NEFA, and thyroxine were quantified in plasma samples collected weekly during treatment and during 7 wk before the first estrus. Estrous behavior was detected by radiotelemetry, and luteal activity was determined based on concentrations of progesterone in plasma. All cows were bred by AI between 14 and 20 h after onset of estrus, and pregnancy was assessed at 35 to 55 d after AI by ultrasonography. Cows that calved with a BCS of 4 or 5 had similar endocrine function and reproductive performance at the first estrus. During treatment, H cows gained BW and increased BCS (P < 0.01), and had greater (P < 0.05) concentrations of IGF-I, leptin, insulin, glucose, and thyroxine in plasma than M cows. However, during the 7 wk before the first estrus, plasma concentrations of IGF-I, leptin, insulin, glucose, NEFA, and thyroxine were not affected by time. Cows previously on the H treatment had a shorter (P < 0.01) interval to first postpartum estrus and ovulation, and a larger dominant follicle (P < 0.01) at first estrus, than M cows, but duration of estrus and the number of mounts received were not influenced by nutrient intake. Pregnancy rate at the first estrus was greater (P < 0.03) for H (76%, n = 38) than for M (58%, n = 33) cows. Increased nutrient intake after calving stimulated secretion of anabolic hormones, promoted fat deposition, shortened the postpartum interval to estrus, and increased pregnancy rate at the first estrus. Concentrations of IGF-I and leptin in plasma were constant during 7 wk before the first estrus, indicating that acute changes in these hormones are not associated with the resumption of ovarian function in primiparous beef cows.

The effect of nutrition and metabolic status on the development of follicles, oocytes and embryos in ruminants

“…In cattle, greater nutrient intake after calving increased the concentrations of T4 in the plasma (Ciccioli et al, 2003), similar to the response in non-lactating cows (Delavaud et al, 2002). Follicular fluid from the bovine ovaries contains free fractions of thyroid hormones that suggests a possible role for these hormones in the regulation of follicular function.…”

Increased body condition score through increased lean muscle, but not fat deposition, is associated with reduced reproductive response to oestrus induction in beef cows

“…Lactating beef cows with moderate BCS (BCS = 3) have a greater response to an oestrus induction treatment and greater pregnancy percentage than cows with poor BCS (BCS = 2; de Medeiros-Bastos et al, 2004). In agreement, beef cows gaining 0.90 kg of BW daily during the first 71 days postpartum had shorter anoestrus intervals (100 ± 7 days) than cows gaining only 0.45 kg/day (120 ± 7 days; Ciccioli et al, 2003).…”

“…Lactating beef cows with moderate BCS (BCS = 3) have a greater response to an oestrus induction treatment and greater pregnancy percentage than cows with poor BCS (BCS = 2; de Medeiros-Bastos et al, 2004). In agreement, beef cows gaining 0.90 kg of BW daily during the first 71 days postpartum had shorter anoestrus intervals (100 ± 7 days) than cows gaining only 0.45 kg/day (120 ± 7 days; Ciccioli et al, 2003).The mechanisms by which static and dynamic changes in energy reserves affect reproductive function in beef cows involve changes in IGF-I, insulin and leptin (Hess et al, 2005;Crowe, 2008). Increases in a cow's nutrient intake (Bossis et al, 2000) and energy reserves (León et al, 2004) augments IGF-I and insulin concentrations in the blood.…”

“…Moreover, changes in energy reserves during the postpartum period and body condition score (BCS; i.e. 1 = emaciated and 5 = fat) at the time of breeding are also known to affect reproductive performance (Bossis et al, 2000;Ciccioli et al, 2003;de Medeiros-Bastos et al, 2004). Lactating beef cows with moderate BCS (BCS = 3) have a greater response to an oestrus induction treatment and greater pregnancy percentage than cows with poor BCS (BCS = 2; de Medeiros-Bastos et al, 2004).…”

VALOR NUTRITIVO DE UMA PASTAGEM NATIVA DOMINADA POR Eragrostis plana Nees E SUA RELAÇÃO COM O PERFIL METABÓLICO DE VACAS PRIMÍPARAS SUPLEMENTADAS DA GESTAÇÃO AO PÓS-PARTO

“…Uma ferramenta utilizada para verificar o balanço nutricional dos animais a campo é o perfil metabólico, uma vez que, em algumas situações, os desequilíbrios nutricionais podem influenciar as concentrações sanguíneas de alguns metabólitos (8) . O perfil metabólico se refere ao estudo de alguns componentes hematobioquímicos específicos que servem para avaliar, diagnosticar e prevenir transtornos metabólicos, uma vez que os desequilíbrios nutricionais são de difícil percepção e limitam a produção animal, diminuindo a rentabilidade da empresa pecuária (9) . Neste sentido, é fundamental caracterizar o valor nutritivo dos componentes estruturais do pasto ofertado e correlacioná-los com o perfil proteico-mineral dos animais.…”