Steven I. Paisley

Effects of early- to mid-gestational undernutrition with or without protein supplementation on offspring growth, carcass characteristics, and adipocyte size in beef cattle1

Angus × Gelbvieh cows with 2 to 3 previous pregnancies were used to evaluate effects of maternal nutrient restriction on offspring adipose tissue morphology at standard production endpoints. At 45 d after AI to a single sire, pregnancy was confirmed and cows randomly allotted into groups and fed a control (Con, 100% of NRC recommendations), nutrient-restricted (NR, 70% of Con diet), or nutrient-restricted + protein-supplemented (NRP, 70% of Con + essential AA supply to the small intestine equal to Con) diet. At d 185 of gestation, cows were commingled and received the Con diet thereafter. Bull calves were castrated at 2 mo of age. Calves were weaned at 210 d, backgrounded for 28 d, and then placed in the feedlot for 195 d. Steers and heifers were slaughtered at an average 12th-rib fat thickness of 7.6 mm. Adipose tissue from selected depots was collected for adipocyte size analysis. There was no significant difference in BW or BCS between Con, NRP, and NR cows at d 45 of gestation, which averaged 489.7 ± 17.7 kg and 5.35 ± 0.13, respectively. At d 185 of gestation, Con and NRP groups had similar BW (566.1 ± 14.8 and 550.2 ± 14.8 kg) and BCS (6.34 ± 0.27 and 5.59 ± 0.27), but NR cows exhibited reduced (P < 0.05) BW (517.9 ± 14.8 kg) and BCS (4.81 ± 0.27). Among offspring (steers and heifers) at slaughter, there were no significant differences in BW or organ weights among treatment groups. Yield grade was reduced (P < 0.05) and semitendinosus weight/HCW tended (P = 0.09) to be reduced in NR offspring compared with Con and NRP offspring. Average adipocyte diameter was increased (P < 0.05) in subcutaneous, mesenteric, and omental adipose tissue and tended (P = 0.09) to increase in perirenal adipose tissue in NR compared with Con offspring with NRP offspring adipocyte diameter being either intermediate or similar to Con calves. The adipocyte size alterations observed in NR offspring were confirmed by DNA concentration of the adipose tissue depots. There also was an increased mRNA expression (P < 0.05) of fatty acid transporter 1 in subcutaneous adipose tissue from NR offspring compared with Con and NRP offspring. Nutritional restriction during early and mid gestation increased or tended to increase (P < 0.09) adipocyte diameter in all adipose tissue depots in finished steer and heifer calves.

Optimal Stocking Density for Dual-Purpose Winter Wheat Production

Dual-purpose winter wheat production is an important economic enterprise in the southern Great Plains of the United States. Because of the complex interactions involved in producing wheat grain and beef gain from a single crop, stocking density is an important decision. The objective of the research is to determine the stocking density that maximizes expected net returns from dual-purpose winter wheat production. Statistical tests rejected a conventional linear-response plateau function in favor of a linear-response stochastic plateau function. The optimal stocking density of 1.48 steers/ha (0.60 steers/acre) is 19% greater with a stochastic than with a nonstochastic plateau.

Small intestinal growth measures are correlated with feed efficiency in market weight cattle, despite minimal effects of maternal nutrition during early to midgestation.

We hypothesized that gestational nutrition would affect calf feed efficiency and small intestinal biology, which would be correlated with feed efficiency. Multiparous beef cows (n = 36) were individually fed 1 of 3 diets from d 45 to 185 of gestation: native grass hay and supplement to meet NRC recommendations (control [CON]), 70% of CON NEm (nutrient restricted [NR]), or a NR diet with a RUP supplement (NR+RUP) to provide similar essential AA as CON. After d 185 of gestation, cows were managed as a single group, and calf individual feed intake was measured with the GrowSafe System during finishing. At slaughter, the small intestine was dissected and sampled. Data were analyzed with calf sex as a block. There was no effect (P ≥ 0.33) of maternal treatment on residual feed intake, G:F, DMI, ADG, or final BW. Small intestinal mass did not differ (P ≥ 0.38) among treatments, although calf small intestinal length tended (P = 0.07) to be greater for NR than NR+RUP. There were no differences (P ≥ 0.20) in calf small intestinal density or jejunal cellularity, proliferation, or vascularity among treatments. Jejunal soluble guanylate cyclase mRNA was greater (P < 0.03) for NR+RUP than CON and NR. Residual feed intake was positively correlated (P ≤ 0.09) with small intestinal mass and relative mass and jejunal RNA content but was negatively correlated (P ≤ 0.09) with jejunal mucosal density and DNA concentration. Gain:feed was positively correlated (P ≤ 0.09) with jejunal mucosal density, DNA, protein, and total cells and was negatively correlated (P ≤ 0.05) with small intestinal relative mass, jejunal RNA, and RNA:DNA. Dry matter intake was positively correlated (P ≤ 0.09) with small intestinal mass, relative mass, length, and density as well as jejunal DNA and protein content, total cells, total vascularity, and kinase insert domain receptor and endothelial nitric oxide synthase 3 mRNA and was negatively correlated (P = 0.02) with relative small intestinal length. In this study, calf performance and efficiency during finishing as well as most measures of small intestinal growth were not affected by maternal nutrient restriction during early and midgestation. Results indicate that offspring small intestinal gene expression may be affected by gestational nutrition even when apparent tissue growth is unchanged. Furthermore, small intestinal size and growth may explain some variation in efficiency of nutrient utilization in feedlot cattle.

A Multi-Period Analysis of Two Common Livestock Management Strategies Given Fluctuating Precipitation and Variable Prices

Many areas of the US recently endured a severe drought and management strategies to cope with the lack of forage production varied. A multi-period mathematical model is presented that estimates the outcomes of two common producer responses to changes in precipitation, partial liquidation and purchasing hay, given fluctuating cattle prices over a long term planning horizon. Results were further summarized with regression analysis and selected elasticities were calculated to reflect the sensitivity of outcomes to variability in precipitation and livestock prices. Although little impact was seen from utilizing additional hay as a strategy during drought, producers who follow this strategy are in a position to market more animals immediately post drought in general, resulting in better long run financial outcomes. Elasticity estimates suggest that profitability is more sensitive to variability in prices but that optimal choices of management strategies are more sensitive to variability in precipitation.

Small intestinal, stomach complex, and total gastrointestinal tract masses are decreased relative to body weight in high efficiency steers

Although both scientific and industry interest in feed efficiency of ruminant animals has increased greatly in recent years, physiological mechanisms underlying differences in individual feed efficiency remain largely unknown. The gastrointestinal (GI) tract and liver are not only essential for nutrient acquisition and utilization, but also use 40 to 50% of whole body energy expenditure (Ferrell, 1988). Despite recent research in the area (Basarab et al., 2003; Mader et al., 2009; Meyer et al., 2012), the role of visceral organs, especially that of the GI tract, in feed efficiency is unclear. We hypothesize that a portion of the individual differences observed for feed efficiency can be attributed specifically to GI tract size and function through its energy use and ability to digest and absorb nutrients. The objective of this study was to investigate GI tract and other visceral organ masses in market weight steers classified as high and low efficiency based on finishing period residual feed intake (RFI).