Effects of reduced in utero and post-weaning nutrition on milk yield and composition in primiparous beef cows

Abstract

Development and long-term retention of replacement beef females in a semi-arid environment are of a major concern for extensive livestock producers. Furthermore, the demand of not only producing a thriving, healthy calf, but having sufficient milk to support that first calf is essential. To address this issue, we conducted a 3-year study measuring milk production and milk constituent yields in primiparous beef heifers ( n = 48; 16/year reared under two different feeding regimens) raising steer calves. Cows received 1.8 or 1.2 kg/day winter supplementation for~80 day before parturition and their heifer calves were then randomly assigned to heifer development treatments that provided ad libitum (AL) or 80% (less than ad libitum (LAL)) of ad libitum feed post weaning. Heifers developed on the AL treatment also received 1.8 kg/day winter supplementation for life, whereas heifers developed on the LAL treatment received 1.2 kg/day winter supplementation for life. Milk production of primiparous cows was measured with a portable milking machine every other week from days 27 to 125 postpartum. Milk yield for the 125-day lactation period was calculated from area under the lactation curve approximated by trapezoidal summation. The ANOVA model included in utero winter nutrition, post-weaning heifer development treatment, year and their interaction. Heifers subjected to the AL treatment reached peak milk yield~12.3 day later ( P = 0.02) than heifers receiving LAL treatment. In addition, an in utero nutrition × post-weaning heifer treatment × year interaction existed ( P ⩽ 0.04) for milk peak yield, average daily milk yield (kg/day) and nutrient composition (protein, lactose, fat, solids non-fat, g/day). These interactions manifest as changes in magnitude and rank across the 3 years of the study. Livestock production in extensive environments is subject to variations in seasonal precipitation patterns and quality and quantity of grazeable forage and these fluctuations have a large impact on milk yield. In summary, the gestational nutritional environment of a heifer's mother may interact with the heifer's nutrient consumption during post-weaning growth and the current year to trigger variation in year-to-year milk production.Keywords: heifer development, milk and constituent yield, primiparous beef cow ImplicationsRaising livestock in an extensive rangeland environment relies heavily on the nutritive quality of grazeable forage. However, livestock producers in arid and semi-arid environments often encounter times of the year when grazeable forage quality is inadequate to meet animal requirements. Therefore, producers often resort to supplementing livestock with harvested feeds, which ultimately increases cost of production. A challenge for researchers is to provide producers with new and acceptable approaches to sustain optimal levels of production while ensuring economic feasibility. Present research suggests that obtaining an optimal level of additional feed inputs rather than maximizing intake has a similar impact on primip...

Effects of Reduced <i>in Utero</i> and Post-Weaning Nutrition on Glucose Clearance Measures and Serum Metabolites

“…Serum NEFA concentrations early in postpartum may suggest that MARG in utero treated heifers relied on adipose tissue to meet energy needs but quickly returned to similar concentrations as those observed for ADEQ in utero supplemented cows. In general serum NEFA concentrations declined as the post-partum period progressed until later weeks when forage quality was known to diminish as forges senesced [5]. Results suggest that serum NEFA concentrations increase in later weeks when forage quality is diminished and more prominently used for an energy need.…”

“…Thus, our objective was to evaluate effects The LARRL encompasses 22,500 ha and has an average elevation of 730 m. Average daily temperatures range from −12˚C in January to 24˚C in July with daily maximum temperatures occasionally greater than 37˚C during summer and daily minimum temperature occasionally dropping less than −40˚C during winter. Winter mean temperatures during the study were similar to the long-term average [5]. Predominant grasses at this site include grama (Bouteloua), needle grass (Hesperostipa), and wheatgrass (Pascopyrum; Kuchler, 1964) [6].…”

“…In this effort, less emphasis is on maximizing intake, rather the focus is shifted to supplying nutrients in reduced amounts and allowing the grazing ruminant to adapt and become more efficient at utilizing dietary feedstuffs. In a companion study, Waterman et al, [5] observed no determinantal impact in first parity milk yield when nutritional inputs were lessened during in utero and post-weaning heifer development. The present study evaluates glucose clearance and serum metabolites (urea N, non-esterified fatty acids, and β-hydroxybutyrate) throughout first parity lactation that may be influenced by nutritional regimens implemented during in utero and post weaning development.…”

“…Stocking rate was 1.27 ha/AUM and the quantity of forage available in the 53.8 ha pasture during 128 d that primiparous cows were on trial was in excess of cattle needs. More specific information on forage characteristics and nutritional regime can be obtained in our companion study [5].…”