Diet composition, intake, plasma metabolites, reproductive and metabolic hormones during pregnancy in goats under semi-arid grazing conditions

Abstract

The objective of the study was to determine the chemical composition of the diet, intake and plasma concentrations of glucose, urea and non-esterified fatty acids (NEFA) during pregnancy in goats grazing a thorn scrubland of the semi-arid region of North Mexico. Additionally, monthly changes during pregnancy of plasma concentrations of luteinizing hormone (LH), growth hormone (GH), insulin (INS) and progesterone (P4) were also measured. A herd of 250 goats was bred in August and blood samples were collected from 12 goats at monthly intervals up to December to evaluate plasma glucose, urea, NEFA, LH, GH, INS and P4. Three goats fitted with oesophageal cannulae (38±1·7 kg BW) were used to obtain diet samples during pregnancy. Response variables were analysed by split-plot ANOVA for repeated measures on animals across time. When significant differences were observed among pregnancy months, multiple comparisons were performed using the PROC GLM-PDIFF option of SAS. The response variables organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin, hemicellulose and cellulose differed across pregnancy. Mean values for the whole period were (g/kg DM) 866 (OM), 149 (CP), 524 (NDF), 364 (ADF), 131 (lignin), 160 (hemicellulose), and 233 (cellulose). Mean values for dry matter intake (DMI, kg/day), metabolizable energy intake (MEI, MJ/day) and metabolizable protein intake (MPI, g/day) were 1·2, 8·9 and 74·0, respectively and were different among periods of sampling (P<0·05). Mean plasma glucose concentration was 41±4·3 mg/dl with no significant differences (P>0·05) across pregnancy. Plasma NEFA concentrations increased (P<0·05) at the end of pregnancy (August, 0·396 v. November, 1·27 mM/l). Plasma urea concentrations were higher (P<0·05) in August (26·3 mg/dl) and November (26·2 mg/dl). Serum urea concentrations were related to MPI (r=0·82, P=0·10) and to the undegraded protein absorbed from the duodenum (r=0·79; P=0·07), but not with the rumen NH3-N concentration (r=−0·25; P=0·68). Hormone plasma concentrations differed (P<0·05) across pregnancy. While the largest serum LH concentration (P<0·05) was observed in mid pregnancy (October, 7·8 ng/ml), the lowest value was depicted at the end of gestation (4·8 ng/ml). A similar pattern was observed in plasma P4, with monthly increases from August to November, and a reduction during the last month of gestation (August, 5·6 v. December 2·5 ng/ml). With respect to the metabolic hormones, a negative correlation (−0·23, P=0·05) was observed between GH and INS, with the largest plasma INS levels in mid pregnancy (October 1·9 ng/ml), the lowest INS levels in December, 0·8 ng/ml and the largest serum GH concentration in December, 20·2 ng/ml. Results from the study indicate that DMI, MEI and MPI in grazing goats are useful indicators of the nutritive value of the forage consumed by goats which allowed them to keep an important steroidogenic luteal activity during gestation (P4=5·7±0·82 ng/ml, litter size=1·44 kids). Nonetheless, the observed plasma levels of glucose, urea, NEFA, INS and GH indicate that a schedule of energy supplementation may be outlined to ensure an adequate nutritional status of goats during late pregnancy and early lactation.

Selection for nutrients by pregnant goats on a microphyll desert scrub

“…Comparing the values obtained in this study with those published for goats in the same type of landscape (Juá rez- Reyes et al, 2004 and2008), it seems clear that goats managed to select the most nutritious plant parts and plant speciesduring the dry period in order to maximize the ingestion of protein.…”

“…Considering that the average DM intake of adult pregnant mixed breed grazing goats in this landscape in winter is 1.2 kg per goat per day (Juá rez- Reyes et al, 2004;Cerrillo et al, 2006), the levels of this nutrient in the pregnant goats did not meet late pregnancy requirements (National Research Council (NRC), 2007, based on high physical activity). Thus, it seems that, in this particular environment, pregnant goats that carried their fetuses to term handled ingestion of enough high-quality forage to barely maintain a nutritional status to sustain their fetuses.…”

“…Considering the 1.2 kg DM intake of goats in this landscape (Juá rez-Reyes et al, 2004), the levels of this mineral in forages selected by goats were sufficient to provide maximum weight gain, bone growth and pregnancy of goats (NRC, 2007). P has been identified as the most deficient macromineral in grasses used by cattle in rangelands of Mexico (Kawas et al, 1997) and western parts of the United States (Scrivner et al, 1988;Pinchak et al, 1989;Ganskopp and Bohnert, 2003), but goats in this study used forages with sufficient P to keep the normal development of their fetuses.…”

Levels of hormones and cytokines associated with growth in Honamlı and native hair goats

“…In a study (Juárez-Reyes et al 2004) that examined the effects of semi-arid grazing conditions on metabolic changes in pregnant goats, a negative correlation was determined between serum insulin and GH levels during advanced pregnancy (December) period and the highest serum GH levels were reported as 20.2 ng/ml. In another study examining milk production and breast development, the serum GH levels were reported in the pregnant goats as 3.22±0.05, 2.84±0.1 and 2.75±0.22 ng/ml on prenatal 1, 7 and 14th days, respectively (Zhang et al 2014).…”

Inclusion of maize in the grazing diet of goats during the last 12 days of gestation reinforces the expression of maternal behaviour and selectivity during the sensitive period

“…Throughout the year, goat diets in the grazing areas are composed of about 82% shrubs, 12% herbaceous plants, and 6% grasses (Ramírez et al, 1991). Previous studies have shown that animals from grazing areas consume an average of 135 g crude protein (CP)/kg dry matter (DM) and 2.1 Mcal/d metabolisable energy (ME) (Cerrillo et al, 2006;Juá rez-Reyes et al, 2004).…”