1Facultad de Medicina Veterinaria y Zootecnia, Universidad Juárez del Estado de Durango, Carretera Durango-Mezquital, Km 11.5 Durango, Dgo. 34280, Mexico.
2College of Agriculture and Life Sciences, North Carolina State University, Raleigh, NC, 27695, USA.
3Facultad de Agronomía, Universidad Autónoma de Nuevo León, Monterrery, NL 66450, México.
4Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Monterrery, NL 66450, México.
The objective of this study was to determine the monthly chemical composition of the diet consumed by range goats and plasma concentrations of glucose, urea, non-esterified fatty acids (NEFA), luteinizing hormone (LH), growth hormone (GH), insulin and progesterone (P4) during lactation (January–June). Three esophageally-cannulated female goats and twelve intact female goats (38±1.7 kg BW) were used to obtain extrusa and blood samples, respectively. Body weight decreased (P<0.05) by 12.5% during the period from January to May, whereas, in June goats lost 250 g d−1. There was a fall in nutrient density during May and June. With the exception of progesterone (0.1–0.6 ng ml−1), LH (7.1–11.0), GH (22.8–30) and insulin (0.6–1.8) increased (P<0.05) as lactation period progressed. It is concluded that plasma metabolite concentrations suggested that an energy supplementation schedule might be necessary during the early lactation periodof goats. In addition, if harsh climatic conditions appear at the end of lactation, an increment of 70% in their energy maintenance requirements might be considered to avoid weight losses and to improve body condition of goats prior to breeding season.
Chemical composition, diet, blood metabolites, lactation, plasma hormones, range goats
