Late gestational nutrient restriction in primiparous beef females: nutrient partitioning among the dam, fetus, and colostrum during gestation

Abstract

Fall-calving primiparous crossbred beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Heifers were individually-fed chopped poor quality hay and supplemented to meet targeted nutritional planes based on estimated hay intakes. Dam BW, BCS, backfat, and metabolic status were determined pre-treatment, every 21 d (BW and metabolic status) or 42 d (BCS and backfat) during gestation, and post-calving. At birth, calf BW and size were measured, and total colostrum from the most full rear quarter was collected pre-suckling. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Gestational metabolites included day and nutritional plane × day as repeated measures. During late gestation, CON dams gained (P < 0.01) maternal (non-gravid) BW and maintained (P ≥ 0.17) BCS and backfat, while NR dams lost (P < 0.01) maternal BW, BCS, and backfat. Circulating glucose, urea N, and triglycerides were less (P ≤ 0.05) in NR dams than CON at most late gestational timepoints after treatment initiation. Circulating non-esterified fatty acids were greater (P < 0.01) in NR dams than CON. Post-calving, NR dams weighed 63.6 kg less (P < 0.01) and were 2.0 BCS less (P < 0.01) than CON. At 1 h post-calving, NR dams had less (P = 0.01) plasma glucose and tended to have less (P = 0.08) plasma triglycerides than CON. Nutrient restriction did not affect (P ≥ 0.27) gestation length, calf birth weight, or calf size at birth. Colostrum yield was 40% less (P = 0.04) in NR dams than CON. Protein and immunoglobulin concentrations were greater (P ≤ 0.04), but free glucose and urea N concentrations were less (P ≤ 0.03), in colostrum of NR dams than CON. Colostrum total lactose, free glucose, and urea N were less (P ≤ 0.03) in NR dams than CON, but total protein, triglycerides, and immunoglobulins were not affected (P ≥ 0.55). In summary, beef heifers experiencing late gestational nutrient restriction prioritized partitioning nutrients to fetal growth and colostrum production over maternal growth. During undernutrition, fetal and colostral nutrient demands were largely compensated for by catabolism of maternal tissue stores.

Nutrient restriction during late gestation reduces milk yield and mammary blood flow in lactating primiparous beef females

“…We reported that calf birth weight was not affected ( P = 0.72; 29.9 vs. 30.7 ± 1.7 kg) by late gestational nutritional plane ( Redifer et al, 2023 ). With CON and NR dams combined, calf birth weight had a moderate relationship ( r = 0.40 to 0.53; P ≤ 0.05) with milk weight on days 21, 42, 63, 84, and 105 of lactation, but calf birth weight was not correlated ( r = 0.30; P = 0.14) with milk weight on day 147 of lactation.…”

“…We reported that nutrient restricted dams weighed 63.6 kg less and were 2.0 BCS lower than controls post-calving, but calf BW and size at birth were not affected by late gestational nutrient restriction ( Redifer et al, 2023 ). Nutrient restricted dams produced 40% less colostrum, yet it was generally more concentrated so that total colostral nutrients and immunoglobulins, except lactose, were similar ( Redifer et al, 2023 ).…”

“…Beginning on day 274 of gestation, heifers were closely monitored 24 h per day by trained personnel to ensure the time of calving was observed. Peripartum dams were managed as described in Redifer et al (2023) .…”

“…Data reported here are from an intensive experiment to determine the effects of late gestational nutrient restriction in individually-fed first-parity beef females on prenatal and postnatal nutrient availability and utilization by their calves. We reported that maternal growth was slowed for nutrient restricted heifers during late gestation, and they mobilized maternal stores so that fetal growth was spared ( Redifer et al, 2023 ). Additionally, nutrient restricted dams produced less colostrum, but it was more concentrated so that total colostral nutrients and immunoglobulins, except lactose, were similar ( Redifer et al, 2023 ).…”

“…We reported that maternal growth was slowed for nutrient restricted heifers during late gestation, and they mobilized maternal stores so that fetal growth was spared ( Redifer et al, 2023 ). Additionally, nutrient restricted dams produced less colostrum, but it was more concentrated so that total colostral nutrients and immunoglobulins, except lactose, were similar ( Redifer et al, 2023 ). We hypothesized that dams nutrient restricted during late gestation then fed to meet estimated nutrient requirements during lactation would have decreased milk production; thus, postnatal nutrient availability for their calves would be reduced.…”