PSXII-25 Effects of level and source of dietary forage on performance of lactating Alpine goats

Thirty-two primiparous and 32 multiparous Alpine goats consumed diets varying in level and source of forage to determine influences on lactation performance. Diets were 40, 50, 60, and 70% forage (40F, 50F, 60F, and 70F, respectively), with forage in 60F and 70F being coarsely ground grass hay (primarily orchardgrass) and that in 40F and 50F cottonseed hulls, alfalfa pellets, and wheat hay. Initial body weight was 56.1±1.22 and 58.3±1.33 kg for primiparous and multiparous goats, respectively. Diets were 15.7–16.1% crude protein, 40.5, 45.9, 57.1, and 59.6% neutral detergent fiber (NDF), 6.1, 7.4, 4.6, and 5.0% acid detergent lignin, 10.0, 15.8, 50.1, and 55.5% particle retention on a 19-mm sieve, and 28.1, 32.4, 41.9, and 43.2% physically effective NDF for 40F, 50F, 60F, and 70F, respectively. The experiment started at 14 days-in-milk and lasted 16 wk. Average daily gain was similar (P > 0.05) among treatments (-23, -33, -28, and -28 g; SEM=1.11), but dry matter intake [(DMI) 2.71, 2.75, 1.96, and 1.95 kg/d, SEM=0.133] and milk yield (2.82, 2.71, 2.23, and 2.10 kg/d; SEM=0.157) were lower (P < 0.05) for the 2 diets highest in forage. Treatments affected (P < 0.05) milk fat (3.16, 3.37, 2.93, and 2.97%; SEM=0.120) and protein concentrations (2.62, 2.69, 2.58, and 2.52% for 40F, 50F, 60F, and 70F, respectively; SEM=0.042). Milk energy yield was greater (P < 0.05) for the 2 diets highest in concentrate (7.51, 7.45, 5.68, and 5.34 MJ/d; SEM=0.471), although relative to DMI yield was not affected (P > 0.05) by diet (2.94, 2.95, 2.76, and 2.74 MJ/kg for 40F, 50F, 60F, and 70F, respectively (SEM=0.164) and was greater (P < 0.05) for multiparous vs. primiparous goats (2.64 and 3.05 MJ/kg; SEM=0.116). In conclusion, lactational performance of Alpine goats in early to mid-lactation will be constrained with diets high in forage of moderate quality and large particle size.

PSXIII-28 Late-Breaking: Lactational performance of dairy cows receiving supplemental His: A meta-analysis

The objective of this meta-analysis was to examine the effect of supplemental histidine (His) on dry matter intake (DMI), milk (MY) and energy-corrected milk (ECM) yields, and milk components in lactating dairy cows. A comprehensive meta-analysis was performed to data from 20 studies published in peer-reviewed journals between 1999 and 2021. In 12 of the studies His was supplemented to the diet as rumen-protected His and in the remaining experiments free His was infused into the abomasum (5 experiments), the jugular vein (2 experiments) or the duodenum (1 experiment) of the cows. The diets were based on corn silage in 60% and on grass silage in 40% of the studies. In studies where data were available (13 out of 20), metabolizable protein supply was estimated to be on average 98% (min = 85% and max = 110%) of NRC (2001) requirements. Computations were carried out using Comprehensive Meta-Analysis (V. 3.3.070). Histidine supplementation increased (P < 0.001) plasma His concentration by 59%, compared with control. Dry matter intake and MY increased (P ≤ 0.002) by 0.22 and 0.36 kg/d, respectively, whereas ECM yield tended to increase (P = 0.07) by 0.14 kg/d with His supplemented diets vs. the control. Milk protein concentration was also increased (P = 0.004) by 0.20 %-units, whereas milk fat concentration tended to decrease (P = 0.10) by 0.11 %-units with His supplementation. Further, His increased milk protein and lactose yield (P ≤ 0.05) by 0.31 and 0.14 kg/d, respectively. Overall, based on the available data, His supplementation of lactating dairy cow rations enhanced DMI, MY and milk protein concentration and yield.

Providing domperidone throughout lactation enhances sow lactation performance

The goal of this project was to determine the effects of domperidone given throughout lactation on hormonal and metabolic status, lactational performance, and gene expression in mammary epithelial cells of sows. Second parity sows were divided in two treatment groups: 1) daily intramuscular injections with canola oil (Control, CTL, n = 24), or 2) daily intramuscular injections with 0.5 mg/kg body weight (BW) of domperidone (DOMP, n = 23). Injections were given at 08h05 starting the day after farrowing until weaning. Over the first 4 d of treatment DOMP sows also received 0.5 mg/kg BW of domperidone per os twice daily, whereas CTL sows were fed the vehicle. Litter size was standardized to 11 ± 1 within 24 h of birth and piglets were weighed at birth, 24 h postpartum, and on days 7, 22 (weaning on day 23), 35 and 56. Sow feed intake was recorded daily. Representative milk samples were obtained aseptically on day 21 of lactation from 15 sows per treatment for compositional analyses and milk fat globules were used to measure mRNA abundances of various genes. Jugular blood samples were obtained from all sows on days 2, 8, 16 and 23 of lactation to measure concentrations of prolactin, insulin-like growth factor-1 (IGF-1), leptin, adiponectin, insulin, glucose, urea and free fatty acids (FFA). Concentrations of prolactin (P < 0.001) and FFA (P < 0.01) were increased in DOMP compared with CTL sows, whereas concentrations of insulin were decreased (P < 0.05). Urea concentrations were increased by treatment (P < 0.05) on days 16 and 23 of lactation, and those of IGF-1 were increased (P < 0.01) on day 16. Piglets from DOMP sows were heavier than those from CTL sows on day 22 (P < 0.01). Milk composition was unaffected by treatment. The mRNA abundance in milk fat globules for casein beta and whey acidic protein were lower (P ≤ 0.05) in DOMP than CTL sows. The long form of the prolactin receptor and the signal transducer and activator of transcription 5A mRNA abundances tended to be lower (P < 0.10) in DOMP than CTL sows. In conclusion, hyperprolactinemia induced by domperidone during lactation affected the endocrine and metabolite status of sows and stimulated growth of their suckling piglets.

Effect of Thyromimetic GC-1 Selective Signaling on Reproductive and Lactational Performance in the Hypothyroid Rat

<b><i>Introduction:</i></b> The potential of the thyroid hormone receptor β (TRβ1) selective analog GC-1 has been widely proven in animal models and humans. However, its effect on the reproductive stage of the female rat has not been evaluated. <b><i>Methods:</i></b> The effect of the administration of GC-1 or equimolar doses of triiodothyronine (T3) was evaluated on the reproductive performance of the hypothyroid female rat and the indirect effect on pup thyroid status, weight, and survival. <b><i>Results:</i></b> Hypothyroidism reduced the number of embryos implanted in the uterus, whereas T3 and GC-1 treatment in hypothyroid females reestablished the number of implanted embryos to normal. Initiation of labor was delayed by hypothyroidism, and T3 replacement treatment reinstated the normal timing of parturition. The administration of GC-1 alone to the lactating mother did not affect pup survival, weight, or thyroidal status. <b><i>Conclusions:</i></b> Our findings show the differential effect of thyroid hormone selective signaling during gestation and the indirect exposure of the pups; we also emphasize the plausible use of GC-1 for treatment of hypothyroid mothers during the lactation period.