A study was conducted to evaluate late gestation maternal nutrient restriction (NR) with or without protein supplementation on endocrine regulation in newborn beef calves. This study used multiparous cows (4 and 5 years of age, n = 57) randomly assigned to one of three treatments for the last 100 days of gestation. The control (Con; n = 19) cows were fed to increase body condition score, whereas the NR (n = 19) and NR with protein supplement (NRS, n = 19) cows were fed to lose 1.2 ± 0.2 body condition score units during the last 100 days of gestation. Control cows were allowed ad libitum access to tall fescue/crabgrass paddock and, when grazing became insufficient, ad libitum hay was provided along with 1.3 kg of corn gluten feed 5 days/wk. Tall fescue paddocks were strip grazed to limit forage availability for NR and NRS. The NRS-treated dams were individually penned and fed 0.45 kg of soybean meal 3 days/wk. As forage became limited, the nutrient-restricted paddocks received limited fescue hay. After parturition cow/calf pairs were moved to a common pasture and received ad libitum silage and high-concentrate feed. Maternal NR regardless of supplementation reduced cow plasma glucose and insulin concentrations during late gestation (P < 0.0001 and P = 0.0051, respectively). Calves from NR dams weighed less at birth than Con calves (P = 0.04), whereas NRS calves were intermediate (33.4 ± 1.2, 35.0 ± 1.3, and 37.2 ± 1.3 kg NR, NRS, and Con, respectively). Plasma glucose concentrations of unsuckled calves at birth were reduced (P = 0.037) in NR and NRS calves compared with Con (67.7 ± 6.5 and 60.1 ± 6.9 vs. 83.7 ± 6.1 mg/dL, respectively). At birth, Con and NRS calves had increased (P = 0.0037) plasma leptin concentrations compared with NR calves, whereas calf plasma cortisol concentrations were greater for the nutrient-restricted groups than the Con group (treatment × day P = 0.0135). Plasma IgG concentrations from calves at 5 days of age were similar (P = 0.701) between maternal late gestation treatments. This research reports that late gestation NR reduces postnatal calf birth weight, plasma glucose and leads to reduced plasma leptin. Maternal protein supplementation appears to partially alleviate the effects of late gestation NR on reducing plasma leptin, birth weight, and growth rate from Day 30 of age to weaning.

The aim of this study is to determine the effects of early and mid-gestation nutrient restriction on maternal metabolites and foetal growth. Primiparous Angus cows were synchronized and inseminated with semen from one sire. Dietary treatments were: control to gain 1 kg/week (CON) or 0.55% maintenance energy and CP requirements (nutrient restricted; NR). A subset of dams was fed NR (n=8) or CON (n=8) from days 30 to 110 of gestation. Another group was fed CON (n=8), days 30 to 190; NR (n=7), days 30 to 110 followed by CON days 110 to 190; or CON, (n=7) days 30 to 110 followed by NR days 110 to 190. Cows were harvested at days 110 or 190 of gestation, when foetal measurements and samples were collected. Cows that were NR during days 30 to 110 or 110 to 190 of gestation lost significant BW and body condition score (P<0.001), this was associated with reduced plasma glucose during NR (P<0.002). Foetal weights, empty foetal weights, abdominal and thoracic circumferences were all reduced (P<0.03) in day 110 NR animals. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.01) in NR day 110 female foetuses compared with CON foetus. Maternal serum triglycerides at day 110 of gestation were decreased (P<0.05) in NR dams, whereas foetal serum triglycerides were increased (P<0.05) in response to maternal NR. Foetal weights tended to be reduced (P=0.08) in NR/CON and CON/NR v. CON/CON cattle at day 190 of gestation. Empty foetal weights, abdominal and thoracic circumferences were reduced (P⩽0.03) in NR/CON and CON/NR v. CON/CON cattle. Brain weight as a percentage of empty foetal weight was increased (P<0.001) in NR/CON and CON/NR v. CON/CON cattle. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.003) in NR/CON and CON/NR v. CON/CON cattle. Maternal serum triglycerides at day 190 of gestation were decreased (P<0.05) in association with maternal NR. Foetal serum triglycerides at day 190 of gestation were increased (P<0.05) in response to maternal NR during early gestation but decreased by NR in mid gestation compared with CON foetuses. The data show that maternal nutrient restriction during early or mid-gestation cause's asymmetrical foetal growth restriction, regardless if the restriction is preceded or followed by a period of non-restriction.

This study's objective was to determine if nutrient restriction during late gestation affected beef heifer feed intake, body weight (BW) gain and endocrine regulation during a 10-week feeding trial. During the last 100 days of gestation, control (CON) dams were fed to increase body condition score (BCS). Whereas, nutrient-restricted dams (NR) and NR dams protein supplemented 3 days/week (NRS) were fed to decrease BCS by 1.2. After parturition, all cow-calf pairs were moved to a common pasture and fed in excess of requirements until weaning. At 15 months of age, heifers were randomly sorted into two pens and adjusted to a commercial total mixed ration over a 2-week period. Blood samples and BW were taken at the initiation of feeding and on a biweekly basis for the duration of the feeding trial. Feed intake was monitored for 10 weeks using a GrowSafe System. After 10 weeks, an intravenous glucose tolerance test (IVGTT) was performed on 21 randomly subsampled heifers. During the feeding trial, NR heifers consumed more feed than CON and NRS heifers. Heifers from NR dams tended to increase BW compared to NRS and CON heifers when adjusted for initial BW. Heifers from NR and NRS dams had a greater increase in BCS compared to heifers from CON dams. Plasma glucose and insulin concentrations during the feeding trial increased in NR heifers compared to the other groups beginning at 2 and 4 weeks respectively. Plasma leptin concentrations were increased in the NR and NRS heifers compared to the CON heifers beginning at week 4 of feeding. During the IVGTT at the conclusion of the feeding challenge, plasma glucose and insulin were increased in NR heifers compared to other treatment groups. These results show that nutrient restriction during late gestation alters appetite and endocrine regulation in heifer offspring.

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