Net mineral requirements of dairy goats during pregnancy.

Mineral requirements of pregnant dairy goats are still not well defined; therefore, we investigated the net Ca, P, Mg, Na and K requirements for pregnancy and for maintenance during pregnancy in two separate experiments. Experiment 1 was performed to estimate the net Ca, P, Mg, Na and K requirements in goats carrying single or twin fetuses from 50 to 140 days of pregnancy (DOP). The net mineral requirements for pregnancy were determined by measuring mineral deposition in gravid uterus and mammary gland after comparative slaughter. In total, 57 dairy goats of two breeds (Oberhasli or Saanen), in their third or fourth parturition, were randomly assigned to groups based on litter size (single or twin) and day of slaughter (50, 80, 110 and 140 DOP) in a fully factorial design. Net mineral accretion for pregnancy did not differ by goat breed. The total daily Ca, P, Mg, Na and K requirements for pregnancy were greatest in goats carrying twins (P<0.05), and the requirements increased as pregnancy progressed. Experiment 2 was performed to estimate net Ca, P, Mg, Na and K requirements for dairy goat maintenance during pregnancy. In total, 58 dairy goats (Oberhasli and Saanen) carrying twin fetuses were assigned to groups based on slaughter day (80, 110 and 140 DOP) and feed restriction (ad libitum, 20% and 40% feed restriction) in a randomized block design. The net Ca, P and Mg requirements for maintenance did not vary by breed or over the course of pregnancy. The daily net requirements of Ca, P and Mg for maintenance were 60.4, 31.1 and 2.42 mg/kg live BW (LBW), respectively. The daily net Na requirement for maintenance was greater in Saanen goats (11.8 mg/kg LBW) than in Oberhasli goats (8.96 mg/kg LBW; P<0.05). Daily net K requirements increased as pregnancy progressed from 8.73 to 15.4 mg/kg LBW (P<0.01). The findings of this study will guide design of diets with adequate mineral content for pregnant goats throughout their pregnancy.

Effects of different supplemental soya bean oil levels on the performance of prepubertal Saanen goats: Oestrogen and progesterone release.

The aim of this study was to investigate the effects of different levels of soya bean oil in the total diet on the growth rate, metabolic changes, and oestrogen and progesterone release in Saanen goats. After dietary adaptation, 21 prepubertal goats (weight of 29.12 ± 0.91 kg, 230 days old) were randomly distributed among three diets of D2: inclusion of 2% soya bean oil in the total diet; D3: basal diet - inclusion of 3% soya bean oil in the total diet; and D4: inclusion of 4% soya bean oil in the total diet. The basal diet (D3) was formulated to promote a daily gain of 0.140 kg. The goats were weighed, and their blood samples were collected weekly. Glucose, cholesterol, triglycerides, total protein, urea, non-esterified fatty acids, beta-hydroxybutyrate, oestrogen and progesterone in the plasma were measured. Prepubertal goats that were fed D4 exhibited a significantly lower dry matter intake, urea and cholesterol levels compared with the goats that were fed D2 and D3. Indeed, goats that were fed D4 displayed a significantly lower final weight than goats that were fed D2 and D3. In contrast, the inclusion of soya bean oil in the diet increased the progesterone and oestrogen concentrations, and goats that were fed D4 released a significantly higher concentration of progesterone than those that were fed D2 and D3. Furthermore, the percentage of goats with a progesterone level greater than 1 ng/ml (functional Corpus luteum) was significantly higher among the goats that were fed D3 and D4 than among those that were fed D2. In this study, although the inclusion of 4% soya bean oil in the diet decreased dry matter intake and growth rate, it increased progesterone concentration and the percentage of goats with a functional Corpus luteum, suggesting that the inclusion of soya bean oil accelerated puberty in prepubertal goats.

Mineral requirements for growth and maintenance of F1 Boer × Saanen male kids.

The objective of this study was to determine the net requirements of minerals for the growth and maintenance of intact male F1 Boer × Saanen goat kids in the initial phase of growth. The following 2 experiments were performed: Exp. 1 was performed to determine the net growth requirements for Ca, P, Mg, Na, and K by F1 Boer × Saanen goat kids from 5 to 25 kg of BW and Exp. 2 was performed to determine the maintenance requirements of F1 Boer × Saanen goats from 15 to 25 kg BW. In Exp. 1, 32 intact male goat kids were distributed in a completely randomized design and mineral body composition was fit to an allometric equation in the form of a nonlinear model. To determine the mineral requirements for maintenance in Exp. 2, 21 intact male goat kids were distributed in a randomized block design, where the goat kids were subjected to 3 levels of feed restriction (0, 30, and 60% feed restriction). At the onset of Exp. 2, 7 goat kids were harvested and used to estimate the initial body composition (15 kg BW). Initial body composition was used to calculate the retention of minerals. The maintenance requirements were estimated by regressions obtained from the retention of minerals in the empty body and the intake of the mineral. The concentration of Ca, P, Na, and K in the empty BW decreased by 11, 13, 26, and 23% with the increase in BW from 5 to 25 kg (P < 0.01). As a consequence, our results showed that net requirements of Ca, P, Mg, Na, and K for weight gain decreased by 27.5, 27.8, 4.25, 43.2, and 39.7%, respectively, with the increase in BW from 5 to 25 kg (P < 0.01). The net requirements (g/kg of ADG) decreased from 9.7 to 7.0 for Ca, 6.5 to 4.7 for P, 0.38 to 0.36 for Mg, 0.88 to 0.50 for Na, and 1.9 to 1.2 for K when BW increased from 5 to 25 kg. The daily net requirements for maintenance per kilogram of BW were 38 mg of Ca, 42 mg of P, 1.6 mg of Mg, 5.0 mg of Na, and 19 mg of K. These results for the nutritional requirements of minerals may help to formulate more balanced diets for F1 Boer × Saanen goat kids in the initial growth phase.

A kinetic model of phosphorus metabolism in growing goats.

The effect of increasing phosphorus (P) intake on P utilization was investigated in balance experiments using 12 Saanen goats, 4 to 5 mo of age and weighing 20 to 30 kg. The goats were given similar diets with various concentrations of P, and 32P was injected to trace the movement of P in the body. A P metabolism model with four pools was developed to compute P exchanges in the system. The results showed that P absorption, bone resorption, and excretion of urinary P and endogenous and fecal P all play a part in the homeostatic control of P. Endogenous fecal output was positively correlated to P intake (P < .01). Bone resorption of P was not influenced by intake of P, and P recycling from tissues to the blood pool was lesser for low P intake. Endogenous P loss occurred even in animals fed an inadequate P diet, resulting in a negative P balance. The extrapolated minimum endogenous loss in feces was .067 g of P/d. The minimum P intake for maintenance in Saanen goats was calculated to be .61 g of P/d or .055 g of P/(kg(.75) x d) at 25 kg BW. Model outputs indicate greater P flow from the blood pool to the gut and vice versa as P intake increased. Intake of P did not significantly affect P flow from bone and soft tissue to blood. The kinetic model and regressions could be used to estimate P requirement and the fate of P in goats and could also be extrapolated to both sheep and cattle.