Effect of Protein Level During Late Gestation on Weight Change and Calving Characteristics of First Calf Heifers

Abstract

AbstractSixty-six Angus x Gelbvieh heifers were used to determine the effects of protein intake during the last one-third of gestation on heifer weight change, body condition score, and calving characteristics. Heifers were randomized to 1 of 12 groups of either five or six animals, then groups were randomized to one of four dietary protein levels with three replications of each diet. Diets were calculated to be isocaloric and to supply either 75, 100, 150, or 200% of NRC protein requirements for heifers in the last one-third of gestation. Experimental diets were fed for 77 d. At 1 wk before the first estimated calving date, all heifers were grouped in one lot and fed a diet calculated to meet NRC requirements for lactating heifers. Heifer weights and body condition scores (1 to 9 scale) were recorded at the beginning and end of the experimental feeding period after 16-h feed removal. Replicate means were analyzed using a general linear model. Protein intake level had no effect (p>0.10) on calf birth weight, weaning weight, adjusted 205-d weight, calving ease score, calf vigor score, or postpartum interval to estrus. Birth weights were 37, 39, 38, and 40 ± 1lb for 75, 100, 150, and 200% protein intake levels (p=0.28), respectively. Dietary protein intake level did not affect heifer weight change (p=0.27) during the study (22, 44, 43, and 36 ± 8lb for 75, 100, 150, and 200% protein intake levels, respectively). Dietary protein treatments also did not affect dystocia (p=0.58) or postpartum interval (P=0.93). In summary, protein intake levels as high as 200% of recommended NRC requirements during late gestation did not affect calving difficulty, birth weight, or postpartum interval to estrus in first-calf heifers.