Effects of the Level and Composition of Concentrate Supplements before Breeding and in Early Gestation on Production of Different Hair Sheep Breeds

SIMPLE SUMMARY: The level of supplementation of low-quality forage diets before and in the early gestation period may influence the performance of different hair sheep breeds. Dorper, Katahdin, and St. Croix sheep consumed wheat straw ad libitum supplemented with 0.15% initial body weight (BW) of soybean meal or a 1:3 mixture of soybean meal and rolled corn at 1% BW for 162 days with 84 or 97 days pre-breeding. Supplement treatment by breed did not generally influence feed intake, BW, body condition and mass indexes, or reproductive performance. Although soybean meal given alone boosted straw intake, it resulted in lower total feed intake, litter size, and total litter birth weight compared with the higher level of supplementation. Body condition score and mass indexes and BW were affected by breed, but reproductive performance was not influenced. Therefore, hair sheep regardless of breed fed low-protein and high-fiber forage such as wheat straw should be supplemented at a higher level with consideration of the inclusion of a feedstuff(s) high in energy along with protein during these physiological periods. ABSTRACT: Female hair sheep, 27 Dorper (DOR), 41 Katahdin (KAT), and 39 St. Croix (STC), were used to determine influences of the nutritional plane before breeding and in early gestation on feed intake, body weight, body condition score, body mass indexes, blood constituent concentrations, and reproductive performance. There were 35 multiparous and 72 primiparous sheep, with initial ages of 5.6 ± 0.25 years and 1.5 ± 0.01 years, respectively (average overall initial age of 2.8 ± 0.20 years). Wheat straw (4% crude protein; dry matter [DM] basis) was consumed ad libitum and supplemented with approximately 0.15% initial body weight (BW) of soybean meal (LS) or a 1:3 mixture of soybean meal and rolled corn at 1% BW (HS; DM). The supplementation period was 162 days, with the breeding of animals in two sets sequentially, with the pre-breeding period 84 and 97 days, and that after breeding began at 78 and 65 days, respectively. Wheat straw DM intake (1.75, 1.30, 1.57, 1.15, 1.80, and 1.38% BW; SEM = 0.112) was lower (p < 0.05), but average daily gain (−46, 42, −44, 70, −47, and 51 g for DOR-LS, DOR-HS, KAT-LS, KAT-HS, STC-LS, and STC-HS, respectively; SEM = 7.3) was greater (p < 0.05) for HS than LS treatment during the supplementation period. Additionally, changes in body condition score during the supplementation period (−0.61, 0.36, −0.53, 0.27, −0.39, and −0.18; SEM = 0.058), and changes in body mass index based on height at the withers and body length from the point of the shoulder to the pin bone (BW/[height × length], g/cm(2)) from 7 days before supplementation (day −7) to day 162 were −1.99, 0.07, −2.19, −0.55, −2.39, and 0.17 for DOR-LS, DOR-HS, KAT-LS, KAT-HS, STC-LS, and STC-HS, respectively; (SEM = 0.297) were affected by supplement treatment. All blood constituent concentrations and characteristics addressed varied with the day of sampling (−7, 14, 49, 73, and 162) as well as the interaction between the supplement treatment and the day (p < 0.05), with few effects of interactions involving breed. Birth rate (66.7, 93.5, 84.6, 95.5, 82.8, and 100.0; SEM = 9.83) and individual lamb birth weight (4.50, 4.61, 4.28, 3.98, 3.73, and 3.88 kg; SEM = 0.201) were not affected by supplement treatment (p = 0.063 and 0.787, respectively), although litter size (0.92, 1.21, 1.17, 1.86, 1.12, and 1.82; SEM = 0.221) and total litter birth weight (5.84, 5.74, 5.92, 7.52, 5.04, and 6.78 kg for DOR-LS, DOR-HS, KAT-LS, KAT-HS, STC-LS, and STC-HS, respectively; SEM = 0.529) were greater (p < 0.05) for HS than for LS. In conclusion, although there was some compensation in wheat straw intake for the different levels of supplementation, soybean meal given alone rather than with cereal grain adversely affected BW, BCS, BMI, and reproductive performance, the latter primarily through litter size but also via a trend for an effect on the birth rate. Hence, the supplementation of low-protein and high-fiber forage such as wheat straw should include a consideration of the inclusion of a feedstuff(s) high in energy in addition to nitrogen.