Effects of Using Dried Distiller’s Grains Plus Solubles in Post-Partum Diets of Beef Cows on Heifer Offspring Reproductive Performance

Primiparous and multiparous, Angus-Simmental cows were used in a complete randomized block design to evaluate the effects of feeding dried distillers grains plus solubles (DDGS) as a primary source of dietary energy, which resulted in varying levels of protein, during early lactation on heifer progeny composition and reproductive performance. Cows were blocked by calf birth weight, cow weight, body condition score, and age and randomly assigned to one of three treatments: 1) a silage-based total mixed ration (TMR; CON); 2) TMR with 2.5 kg/d DM DDGS (MID), or 3) TMR with 4.7 kg/d DM DDGS (HIGH). All diets were formulated to be isocaloric and either meet, or exceed all other nutrient requirements (NRC, 2000) for a postpartum targeted ADG of 0.22 kg. Nineteen days post timed-artificial insemination (TAI) of the dams, cows and heifers were commingled and placed on pasture. Milk samples were collected from the dams at 65.5 ± 10.5 days post-partum (DPP) to determine composition. Following weaning, all heifer offspring were maintained as a group and fed a diet formulated to either meet or exceed all nutrient requirements (NRC, 2000). Blood samples were collected from the heifer offspring on 7d intervals until estrous synchronization and evaluated for progesterone concentration as an indicator of puberty. Heifer offspring were started on a 5-d Co-Synch + CIDR protocol and were bred using TAI. Diameter of the largest antral follicle was determined at TAI via ultrasonography. Data were analyzed using the GLIMMIX and MIXED procedures of SAS. Planned orthogonal contrasts were used to test treatment effects. Milk fat increased as DDGS increased (P ≤ 0.03) and lactose (P ≤ 0.03) was increased in the MID treatment, with HIGH being intermediate and CON the lowest. Milk urea nitrogen (MUN) increased as DDGS increased within the diet (P < 0.001). Heifer offspring final BW (P ≥ 0.27), ADG (P ≥ 0.22) and days of age at puberty (P ≥ 0.39) were not different between treatments. Total antral follicle count differed (P = 0.027) when CON was compared to the average of HIGH and MID, with HIGH highest, MID intermediate and LOW lowest. While not statistically different (P ≥ 0.30), TAI conception rates had a 25% increase for the HIGH treatment when compared to the CON and MID. In summary, feeding dams high levels of DDGS during early lactation resulted in variations in milk composition, without a statistically significant impact on heifer offspring reproduction.