Abstract
The objective of this study was to evaluate the mobilization of nutrients in goats of different gestation types and pregnancy stages. Forty-four Saanen and Oberhasli goats were studied. The goats of each breed and gestation type (single or twin) were slaughtered at different gestational ages (80, 110, and 140 days of pregnancy), forming a completely randomized design in a 2 × 3 × 2 factorial arrangement (two breeds, three gestational ages, and two types of pregnancy). The slaughter procedure involved separating the empty body, mammary glands, uterus with membranes and fetal fluid, and fetus(es). For the females slaughtered at 140 days of pregnancy, blood was collected to analyze metabolites and hormones every 15 days during gestation. The dry matter (DM) intake was lower in goats with twin pregnancies. The relative daily retention rate of the nutrients in the body was positive at 100 days of pregnancy but became negative at 140 days (-0.18±0.25 g DM kg-1 of maternal body d-1) and did not differ with breed or number of fetuses. Fetal growth in twin pregnancies was 66% higher than in single pregnancies. The highest levels of s-hydroxybutyrate and non-esterified fatty acids were observed beginning at 100 days of gestation. Serum total protein and albumin levels decreased after 125 days of gestation. Serum urea levels were reduced after 80 days of gestation. Plasma 17s-estradiol levels increased with the advance of pregnancy, and IGF-1 was highest between 60 and 80 days of gestation. The maternal metabolism throughout pregnancy does not vary with the type of pregnancy, and pregnant goats need greater nutritional intake during the final third of the gestational period regardless of the breed or type of pregnancy.
Highlights
Profound metabolic changes take place in pregnant females, and the physiological mechanisms involved in these changes have primarily been studied for the last six weeks of gestation because this is the period during which approximately 70% of fetal growth and the majority of the development of the glandular and mammary tissues occur, contributing to an increase in energy requirements (Conway et al, 1996; NRC, 2007)
The negative energy balance has already been explored in studies of dairy cows, there are currently no studies addressing this physiological process in the goat, which may suffer from an even more marked energy deficit due to its high prolificacy and high incidence of twin births (Amoah et al, 1996)
There was no effect of breed on the calculations used to estimate empty body weight, maternal body, and mammary glands in non-pregnant goats, so the same equation was used for both breeds (Eqs. [2], [3] and [4])
Summary
Profound metabolic changes take place in pregnant females, and the physiological mechanisms involved in these changes have primarily been studied for the last six weeks of gestation because this is the period during which approximately 70% of fetal growth and the majority of the development of the glandular and mammary tissues occur, contributing to an increase in energy requirements (Conway et al, 1996; NRC, 2007). There is a decrease in dry matter intake caused by the compression of the rumen by the fetus and elevated estrogen concentration (Forbes, 2007) This scenario may lead to increased efficiency in nutrient use in the final stage of pregnancy (Bauman and Currie, 1980; Bonnet et al, 2002; Duarte et al, 2013), which may not be sufficient to compensate for the decreased dry matter intake, so the pregnant goat may have a negative energy balance (Bell, 1995). Studies show that there are differences in productive and reproductive traits among dairy goat breeds; Saanen animals show higher precocity, milk yield and lactation longevity, whereas Oberhasli goats display a higher concentration of milk protein and fat (Boichard et al, 1989) These differences among genotypes may indicate different physiological adaptation mechanisms under the same nutritional conditions, especially during pregnancy (Silanikove, 2000; Macciotta et al, 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
