Effect of dried corn distillers grains plus solubles compared to soybean hulls, in late gestation heifer diets, on animal and reproductive performance

¹ Department of Animal and Range Sciences, South Dakota State University Brookings, SD 57007

^* To whom correspondence should be addressed. E-mail: George.Perry{at}sdstate.edu.

	Abstract

Dried distillers grains plus solubles (DDGS) contain fat and undegradable intake protein, both of which have been shown to increase reproductive performance in heifers. Mechanisms leading to enhanced reproduction have not been fully defined. Objectives of this research were to evaluate effects of DDGS in late gestation heifer diets on animal and reproductive performance and on concentrations of GH, IGF-I, and NEFA. Over 2 yr, 201 heifers were randomly allotted to 1 of 2 diets, similar in energy and adequate in degradable intake protein, fed from d 190 of gestation through calving. Diets were grass hay with DDGS or soybean hulls (SBH) and a supplement. Cow BW and BCS were measured from the start of treatment through weaning. Blood samples were collected prepartum on d 71 and 69 of the feeding period and weekly following calving for 4 and 6 wk (d 84 to 105 and d 76 to 111 relative to the feeding period) during yr 1 and 2, respectively. No treatment x year interactions were detected for any of the performance, hormonal, or reproductive dependent variables. Both treatments caused positive BW changes over the feeding period, but DDGS heifers had a greater (P < 0.01) positive BW change compared to SBH heifers. Initial and final BCS and BCS change were similar (P 0.26) between DDGS and SBH. Treatment did not influence (P 0.12) BW or BCS change during the postpartum period. Calving ease, calf vigor, calf birth weight, weaning weight, and ADG (birth to weaning) were similar (P 0.41) between treatments. The proportion of cows that had initiated estrous cycles (P = 0.46) and pregnancy distribution (P 0.21) were similar between treatments. However, a greater (P = 0.04) percentage of DDGS cows became pregnant compared to SBH cows (94 and 84%). In both years, there were no effects of treatment (P 0.17) or treatment x time (P 0.52), but time influenced (P 0.05) concentrations of GH, IGF-I, and NEFA. Concentrations of GH were greater (P 0.05) at calving and decreased through d 4 after calving. Systemic IGF-I concentrations were greater (P < 0.01) around calving and decreased (P < 0.05) through d 8 or 6 (yr 1 and 2) and remained similar (P > 0.10) for the duration of the sampling period. Concentrations of NEFA increased from calving through d 8, and gradually declined through d 20. Prepartum diets containing DDGS, a source of fat and UIP, benefited pregnancy rates in well-maintained, primiparous beef heifers.iets containing DDGS, a source of fat and UIP, benefited pregnancy rates in well-maintained, primiparous beef heifers.

Key Words: beef cattle, dried distillers grains plus solubles, fat, undegradable intake protein, reproduction