Nutrition and suckling are largely recognised as the most important factors affecting the postpartum period and consequently the reproductive efficiency of beef cattle. The aim of this study was to evaluate the effects of body condition score (BCS) and suckling restriction with and without the presence of the calf on milk production, reproductive efficiency and calf performance. Sixty-three crossbred (Angus · Hereford) multiparous cows were managed to maintain different BCS at calving and thereafter (low vs moderate; L, n = 31 and M, n = 32). Within each group of BCS (L and M) at week 9 postpartum (66 AE 0.88 days postpartum) cows were assigned to three suckling treatments (ST): (i) suckling ad libitum (S, n = 20); (ii) calves fitted with nose plates during 14 days remaining with their dams (NP, n = 22); and (iii) calves were completely removed from their dams for 14 days, and thereafter returned (CR, n = 21). Milk production was assessed by milking procedure at Day 65 (the day before onset of ST) and every 20-22 days until the end of the experiment. Cows were bled via jugular venipuncture every 28 days from Day -98 (Day 0 = calving) until Day 66. From Day 66 cows were bled every 7 days until the end of the mating period (Day 128). Concentrations of progesterone, non-esterified fatty acids and b-hydroxybutyrate acid and insulin were measured. Presence of corpus luteum (CL) was recorded and maximum follicle diameter was measured in all cows from the onset of the ST (Day 66) and during the following 4 weeks (until Day 94) in a weekly frequency. At Day 94, more cows (P < 0.001) in NP and in CR had CL compared with S cows (68, 57 and 21% for NP, CR and S, respectively). At that time, more cows in M-BCS presented CL than cows in L-BCS (77 vs 25; P < 0.0001). Within M-BCS, there were no differences in milk production between ST groups, while L-BCS cows with NP or CR produced less milk than S cows. Calf liveweight at weaning was 159.3 AE 3.1, 150.1 AE 2.9 and 147.0 AE 3.1 kg for S, NP and CR, respectively (P < 0.001). Suckling restriction with and without the presence of the calf had similar effects on reproductive performance, milk production and calf growth, while BCS interacted with ST to influence milk production. These results indicate that temporary suckling restriction could be an excellent management tool to increase reproductive performance of cows in moderate condition.

Our objective was to evaluate the metabolic, endocrine and hepatic mRNA profiles through the gestation-lactation cycle in purebred (PU: Angus and Hereford) and crossbred (CR: reciprocal F1 crosses) mutliparous beef cows (n = 32), grazing on two herbage allowances of native pastures (2.5 v. 4 kg dry matter/kg BW; LO v. HI) and their associations with cow's productive performance (calf birth weight, milk production and commencement of luteal activity). Cow BW, body condition score (BCS) and blood samples were collected monthly, starting at − 165 days relative to calving (days), and every 2 weeks after calving until +60 days of lactation. Liver biopsies were collected at − 165, − 75, − 45, − 15 ± 10, and +15 and +60 ± 3 days. Metabolic, endocrine and hepatic gene expression profiles, and calf birth weight, milk yield and postpartum commencement of luteal activity were evaluated. Overall, the most pronounced changes in metabolic, endocrine and hepatic gene expression occurred during winter gestation (−165 to − 45 days), when all cows experienced the onset of a negative energy balance (decreased BCS, glucose and insulin, and increased non-esterified fatty acid concentrations, P < 0.008). Concentrations of insulin and IGF-I were greater (P < 0.037) in HI than in LO cows. However, serum IGF-I concentrations and hepatic growth hormone receptor (GHR) and IGF1 mRNA decreased (P < 0.05) during the winter gestation period only in HI cows. Although IGF-I concentrations decreased (P < 0.05) during the early postpartum (−15 v. + 15 days) for all cows, the typical molecular mechanism that control the uncoupling of the growth hormone-IGF1 axis during the transition period of the dairy cattle (reduced hepatic GHR1A and IGF-I mRNA) was not observed in this study. The hepatic mRNA expression of key transcripts involved in gluconeogenesis and fatty-acid oxidation were upregulated (P < 0.05) during winter gestation (from − 165 to − 45, − 15 or +15 days, depending on the cow groups). Particularly, acyl-CoA oxidase-1 mRNA was greater for CR than for PU cows during winter gestation (−75 and − 45 days), and fibroblast growth factor-21 mRNA was downregulated (P < 0.01) only for HI cows during the transition (−15 v. 15 days) and lactation period (+15 to +60 days, P < 0.01). These results, together with the greater BCS, estimated energy intake, increased milk yield and shorter commencement of luteal activity in HI than in LO, and in CR than in PU cows (P < 0.018), would indicate that HI and CR cows were able to adapt more efficiently to changes in nutrient and energy supply through the gestation-lactation cycle.

-The objective of this study was to evaluate the effect of a short-term supplementation with rice bran (2 kg/cows/day) on the endocrine and metabolic profiles and hepatic gene expression, associated with the reproductive response in beef cows in grazing conditions. Thirty-eight primiparous beef cows (Hereford, Angus and Hereford × Angus) were used in a randomized block design according to genotype, calving date and body condition score at calving (BCS). At 64±14 days postpartum (day 0 of the experiment), cows were assigned to two nutritional treatments: i) control, grazing native pastures (CON, n=19) and ii) supplemented (SUP, n = 19) for 21 days (days 1 to 21 of the experiment). Blood samples were collected at 0, 7 and 22 days and liver biopsies were obtained at day 22 to determine the abundance of mRNA of growth hormone receptor (GHR), insulin-like growth factor -I (IGF1), and its binding proteins -2 and -3 (IGFBP2 and IGFBP3), and insulin receptor (INSR) using SYBR-Green real-time RT-PCR with hypoxanthine phosphoribosyltransferase as endogenous control. Short-term supplementation with rice bran did not modify either cow BCS or BW, or calf BW or average daily gain. However, it decreased by 11 days the length of postpartum anestrus of primiparous cows in grazing conditions, associated with increased concentrations of glucose and insulin, and reduced hepatic expression of IGFBP2 mRNA at the end of the experimental period.

The aim of this study was to determine the effect of nutrition during foetal and lactation periods on calf growth and body composition, and their association with changes in metabolic and endocrine profiles during the calf first year of life on purebred (Hereford and Angus) and cross-bred (F1) dam offspring. Forty cross-bred calves and their dams (purebred--PU: Hereford and Angus, and cross-bred--CR: F1) were used in a randomized block design with a factorial arrangement of herbage allowance of native pastures (high: Hi-HA and low: Lo-HA), 4 vs. 2.5 kg dry matter/kg body weight (BW) and dam genotype (PU vs. CR). Calf BW and blood samples were collected monthly from birth to 380±15 days of age, and body composition was estimated by the urea dilution technique at weaning (142±15 days) and 380 days. Calf birthweight did not differ among groups but from birth to 380 days, and BW was reduced (p=0.046) in Lo-PU offspring. Although Lo-CR calves achieved similar BW than Hi-PU and Hi-CR offspring, they showed an increased fat in detriment of lean tissue deposition. At birth, plasma total protein was less (p=0.04), while plasma glucose, insulin or IGF-I tended or were greater (p<0.072) in Hi-HA than Lo-HA calves. Greater (p<0.03) plasma total protein and/or glucose concentrations during the first months of lactation were observed in CR offspring associated with the greater dam milk production. Although glucose concentrations did not differ among calf groups after weaning, plasma insulin was greater (p=0.004) in Hi-PU than other groups at 380 days. Consistent with the reduced BW, Lo-PU offspring presented the lowest (p=0.026) plasma IGF-I from birth to 380 days. Herbage allowance of native grasslands during calf foetal and lactation periods interacted with maternal heterosis to affect, in the short and/or long term, calf BW or body composition, and metabolic and endocrine profiles.

The effect of shearing ewes at 50 days of gestation on birth and weaning weight, vigour of the lambs in the first hour of life and the survival of single and twin lambs was investigated. Ultrasound pregnancy diagnosis was used to allocate 140 Polwarth ewes on Day 50 of gestation to one of four treatments, including two factors: shearing time (prepartum (PS) and postpartum (U)) and litter size (single (S) and twin (T)) resulting in the following treatments: single-bearing ewes shorn at 50 days of gestation (SPS, n = 39), single-bearing ewes unshorn (SU, n = 40), twin-bearing ewes shorn at 50 days of gestation (TPS, n = 28) and twin-bearing ewes unshorn (TU, n = 33). All ewes grazed together on improved pastures. Body condition score of the ewes was recorded once every 2 weeks from shearing until weaning, and plasma concentration of NEFA in ewes was measured once every 2 weeks from Day 30 postpartum until weaning (Day 104 ± 7). Gestation length, lamb behaviour during the first hour of life, lamb weight at birth and daily weight gain from birth to weaning and lamb survival were measured. Ewe body condition and plasma non-esterified fatty acids concentration was not affected by shearing time or litter size. Birthweight of the lambs was affected by shearing time (P = 0.0002), litter size (P < 0.0001) and sex of the lamb (P = 0.03). Lambs born to PS ewes had higher daily growth rate (P < 0.0001) than lambs born to U ewes (0.149 ± 0.07 vs 0.141 ± 0.07 kg, respectively). Birthweight affected the number of assisted lambs at birth (P = 0.01). Length of gestation was affected by shearing time (P < 0.0001). Sucking ability was improved by shearing time and litter size. Lambs born to PS ewes tried to suck (P = 0.01) and successfully sucked (P = 0.009) before lambs born to U ewes (23.3 ± 2 vs 28.7 ± 2 and 37.6 ± 1 vs 38.4 ± 1 min, respectively). Attempt and success to suck was affected by litter size (P = 0.004 and P = 0.05). TPS-born lambs tried to suck before (P = 0.004) and successfully sucked earlier (P = 0.0004) than TU lambs (26.1 ± 2.5 vs 33.7 ± 2 and 38 ± 1 vs 42.1 ± 2 min, respectively). Shearing time affected lamb survival at 20 days of age (P = 0.04). The improved survival in these lambs, expressed by a higher birthweight and vigour at birth, may be explained by better nutrition in utero in response to shearing during early pregnancy. In contrast to previous research on prepartum shearing, the present experiment shearing was done at 50 days of gestation. Early shearing in gestation might coincide with a period of high cell proliferation, intense vascular development and increased uterine and umbilical blood flows in the placenta which is in rapid development, and may result in improved outcomes when compared with shearing done on Day 70 or later of gestation.