Influence of postweaning feeding management of beef heifers on performance and physiological profiles through rearing and first lactation

Abstract

The aim of this study was to examine the effects of 2 postweaning feeding management approaches (FEED: 0.8 [HIGH] vs 0.6 [MOD] kg/d target ADG) on the performance of heifers of 2 beef breeds (BREED: Parda de Montaña [PA] vs Pirenaica) calving at 2 yr. Twenty-five heifers previously creep fed before weaning (6 mo) were assigned to 2 planes of nutrition from 6 to 15 mo of age. At 15 mo, they were inseminated, and then received similar diets until weaning of their first calf (4 mo postcalving). Several parameters were measured to analyze growth and development (BW; ADG; size measures at 6 mo, 15 mo, calving, and weaning), performance at puberty and first breeding, and dam and calf performance in the first lactation (calving traits, ADG, milk yield). Metabolic (glucose, cholesterol, NEFA, β-hydroxybutyrate, and urea) and endocrine status (IGF-I and leptin) were assessed in plasma samples collected every 3 mo from 6 mo to calving and monthly during lactation. No interaction between BREED and FEED was observed. Heifers from the HIGH feeding treatment had higher postweaning ADG than those on the LOW diet. At 15 mo, they had greater BW, heart girth, and external pelvic area, but they did not differ thereafter. All heifers reached puberty at similar BW (55% mature BW) but different ages. Heifers from the HIGH treatment tended (P < 0.09) to be pubertal earlier, and PA heifers were 1.6 mo younger than Pirenaica heifers (P < 0.05) at puberty. At the time of conception (452 ± 59 kg) and calving (471 ± 51 kg), BW was above common recommendations in all groups. Calving traits and performance in lactation did not differ between feeding treatments. BREED only influenced birth weight; PA calves being heavier (P < 0.05), which resulted in a larger calf/cow BW ratio, but no effect on calving difficulty or subsequent performance. Metabolic substrates and hormones depended mostly on sampling date, which was related to current energy and protein intake. Glucose (P < 0.001), cholesterol (P < 0.001), and IGF-I (P < 0.05) were greater during the postweaning phase in heifers on the HIGH diet, and persistent physiological effects were observed during lactation. Age at puberty was negatively related with IGF-I (r = -0.43, P < 0.001), but not with leptin concentrations. In conclusion, regardless of breed, a moderate growth rate ensured adequate heifer development and performance until the first lactation, whereas no advantage was gained from enhanced postweaning gains.

Effects of maternal subnutrition during early pregnancy on cow hematological profiles and offspring physiology and vitality in two beef breeds

“…No interactions among effects were found. The breed had no significant effects on the calves' metabolite and hormone concentrations, in line with previous studies conducted on cows and calves of the same breeds (Álvarez‐Rodríguez & Sanz, ; Rodríguez‐Sánchez, Sanz, Ferrer, & Casasús, ).…”

Effects of Developmental Programming Caused by Maternal Nutrient Intake on Postnatal Performance of Beef Heifers and Their Calves

“…This could be because the maternal nutrient restriction applied in our study during the first third of pregnancy was not sufficient to induce changes in heifer fertility at first breeding; however, more studies are needed to assess the long-term consequences of a reduced antral follicle count on their lifetime reproductive performance. Regarding the breed, no differences in fertility rate were found between PA and PI heifers in our study, in agreement with previous studies conducted with the same breeds [30].…”

“…However, since females of these breeds reach maturity when they are 4 to 5 years old [29], further studies are needed to determine if the heifer growth delay at weaning would impact the attainment of adult weight and mature size. Regarding breed, PA heifers had higher growth rates during rearing, BCS at calving, and calf LW at weaning than PI heifers, in accordance with previous studies [30], which evidenced similar interbreed differences.…”

“…In the current study, 80% of heifers were pregnant with a single AI, which is a higher pregnancy rate than reported other studies using a similar synchronization protocol [30] or cosynch protocols [42]. This high pregnancy rate could be associated with the optimal body development of heifers at AI (approximately 70% of the mature LW).…”

“…Regarding breed, due to the higher ADG during rearing, PA heifers reached puberty 1 month earlier and 23 kg heavier than PI heifers, although these differences were not significant. In a previous study, PA and PI heifers reached puberty at a similar LW, but two months earlier than in our study due to the fact of their higher growth rates after weaning [30].…”