Nutrition, reproduction, production and health aspects of goats under different production systems in northern Mexico

Information is sparse on the relationship between nutrition and many environmental factors on performance of goats, a species of considerable economic importance in Mexico and many other countries. This thesis begins to address some of these deficiencies. The diets selected by esophageally fistulated indigenous goats grazing on a desert grassland were determined throughout the year. Except during April browse constituted over 80% of the goats' diet. Goats showed the highest preference for Atriplex canescens, Sphaeralcea angustifolia and Buddleja scordioides. Levels of protein were inadequate for pregnancy and lactation. Phosphorus and energy intake were always inadequate even for maintenance. In another study, protein, calcium and phosphorus levels in diets selected by goats grazing on a shrubland community in excellent condition varied little during summer and fall. In another study pen-fed Nubian goats showed sexual activity year-round; however fertility was significantly lower in goats bred during the first trimester of the year. Variation in prolificacy over the year was not significant. Rainfall and temperature were significantly correlated with fertility. Semen characteristics of Nubian, Alpine and Granadino bucks kept under semi-confinement conditions did not differ among breeds. Sperm motility was the only characteristic affected by the season of the year. In another study it was found that Nubian, Saanen, Toggenburg and 3/4 Nubian x 1/4 local kids were significantly heavier at birth than Granadino, Alpine and 3/4 Alpine x 1/4 local goats. Single kids were significantly heavier than kids from multiple births. In another study crossbred goats (indigenous x dairy breeds) grazing on range, produced 140 kg of milk in a 6-month lactation. Milk production was highest in the fourth lactation. Body weight before kidding and parity of dam accounted for 44% of the total variation in lactation yield. Litter traits were positively correlated with the doe's parity. Overall mortality of goats under semi-confinement conditions was 21% per year. The youngest animals had a lower risk of dying due to pneumonia than adult goats. The youngest animals were at increased risk of dying due to enteritis and pneumoenteritis. Seasonal patterns were evident in the rate of mortality due to enteritis.