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This study aimed to assess the impact of protein supplementation and its interaction with calf sex (CS) on the performance, metabolism and physiology of pregnant beef cows. Fifty‐two multiparous Zebu beef cows carrying female (n = 22) and male (n = 30) fetuses were used. Cows were individually housed from day 100 to 200 of gestation and randomly assigned to restricted (RES, n = 26) or supplemented (SUP, n = 26) groups. The RES cows were ad libitum fed a basal diet (corn silage + sugarcane bagasse + mineral mixture), achieving 5.5% crude protein (CP), while SUP cows received the same basal diet plus a protein supplement (40% CP, at 3.5 g/kg of body weight). All cows were fed the same diet during late gestation. Differences were declared at p < 0.05. No significant interaction between maternal nutrition and calf sex was found for maternal outcomes (p ≥ 0.34). The SUP treatment increased the total dry matter (DM) intake (p ≤ 0.01) by 32% and 19% at mid‐ and late‐gestation respectively. The total tract digestibility of all diet components was improved by SUP treatment at day 200 of gestation (p ≤ 0.02), as well as the ruminal microbial CP production (p ≤ 0.01). The SUP treatment increased (p ≤ 0.03) the cows' body score condition, ribeye area, the average daily gain (ADG) of pregnant components (PREG; i.e., weight accretion of cows caused by pregnancy) and the ADG of maternal tissues (i.e., weight accretion discounting the gain related to gestation) in the mid‐gestation. The SUP cows exhibited a lower maternal ADG (p < 0.01) compared to RES cows in late pregnancy. There was a 24% additional gain (p < 0.01) in the PREG components for SUP cows during late gestation, which in turn improved the calf birthweight (p = 0.05). The uterine arterial resistance and pulsatility indexes (p ≤ 0.01) at mid‐gestation were greater for RES cows. In conclusion, protein supplementation during mid‐gestation is an effective practice for improving maternal performance, growth of the gravid uterus and the offspring's birth weight. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of Vitamin A (VA) injection on the growth performance and carcass traits of Nellore × Angus crossbred steers and heifers. For that, the same sire inseminated Nellore cows from two artificial insemination (AI) groups were randomly assigned to one of three treatments at 250 d of gestation: no VA injection (Control); VA injection in pregnant cows at 250 d of gestation (VAcow; 2,000,000 IU single dose); VA injection in newborn calves at birth and 60 d of age (VAcalf; 200,000 IU each dose). Cowcalf pairs were kept in the same paddock, and calves received creep-feeding supplementation from 90 d of age to weaning. After weaning, steers and heifers [n = 36; body weight (BW) 213 ± 25.7 kg] were stratified by treatment and BW and allotted into 16 pens. After 207 d of feeding (77 d of growing diet + 130 d of finishing diet), steers and heifers were slaughtered at a commercial abattoir. Data were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of VA injection, sex, and VA injection*sex interaction. The random effects were animal, AI group, and cow parity. Average daily gain before weaning ( P < 0.01) and final BW in the finishing phase were greater ( P = 0.04) in VAcow steers compared with heifers from all treatments (Table 1). Vitamin A had a positive impact on weaning BW of male calves and a negative impact on heifers ( P < 0.01). There was no treatment difference ( P = 0.35) in feedlot average daily gain (ADG), but steers had greater ( P = 0.03) ADG compared with heifers. Moreover, VAcow steers had greater dry matter intake (DMI) in the feedlot ( P = 0.04) compared with other treatments, and there was no effect of VA on DMI of heifers. On the other hand, feedlot feed efficiency tended to be greater (P = 0.07) in Control steers compared with other treatments, with no VA effect on heifers too. The ribeye area was greater ( P = 0.04) in VAcow steers than in Control steers and heifers from all treatments. Intramuscular fat content was greater ( P = 0.04) in VAcow steers than in Control and VAcalf steers. However, there was no effect of VA on heifers and VAcow steers. In addition, VAcow treatment tended ( P = 0.08) to increase backfat thickness. In conclusion, VA injection in pregnant cows can be a strategy to improve marbling in steers, but there is no effect on intramuscular fat in heifers. Additionally, VA injection in pregnant cows produced intramuscular content in beef of steers, similar to heifers. [ABSTRACT FROM AUTHOR]

Gestating cows have an increased nutrient demand to meet the needs of developing the fetus and the midgestation is a critical period for the fetal skeletal muscle development. The aim of this study was to evaluate the skeletal muscle transcriptome in the progeny as a function of the maternal protein nutrition during mid-gestation. Eleven Tabapuã cows and their male calves were used in this study. In the first third of gestation (0 to 100 days of gestation; dg), all cows were kept on pasture. From 100 to 200 dg, the control group (CTRL; 7 animals) received a basal diet achieving 5.5% crude protein (CP), whereas the supplemented group (SUPPL; 4 animals) received a basal diet plus protein supplementation (40% CP). After 200 dg, all animals received the same diet. Weaning was performed at 205 ± 7.5 days of age and animals were kept on pasture until reaching 240 days of age, when they were transferred to a feedlot. Muscle samples were collected at 260 days of age and RNA was extracted for RNA-seq analysis. Gene expression data was analyzed with a negative binomial model to identify (q-value = 0.05) differentially expressed genes (DEG) between treatments. A total of 716 DEG were identified (289 DEG up-regulated and 427 down-regulated in SUPPL group; q-value = 0.05). From the 10 most significant down-regulated DEG in the SUPPL group, two genes associated with apoptotic process were identified: MAPK8IP1 and GRINA, with log2 Fold-Changes (log2FC) of 1.04 and 0.49, respectively. From the 10 most significant up-regulated DEG in the SUPPL group, mTOR was identified, with log2FC=0.31. This is a well-known gene involved in muscle protein synthesis. In conclusion, maternal protein supplementation during mid-gestation affects the expression of genes related to energy metabolism and muscle development, which can lead to long-term impacts on production efficiency. [ABSTRACT FROM AUTHOR]