Effect of indoor energy restriction level and management on beef production in Belgian Blue double-muscled cow-calf pairs.

One hundred and twenty-six cows were involved to investigate the impact of energy (E) restriction (100%, 90%, 80% and 70% of total energy requirements) during the indoor period and two calf management systems (CMS: suckling or rearing). An E restriction during the indoor period resulted in a loss of body weight, even for E100, which was compensated during the re-alimentation period, but body weight remained lower in suckling than in non-suckling cows. The cows yielded 213 full-term gestations and 8 abortions. Abortion was not affected by E (p = 0.187) or CMS (p = 0.804). Calving interval was neither affected by E (p = 0.775) but tended to be longer in suckled cows (p = 0.087). E reduced body weight and body condition score (BCS) at the end of the calving interval, while CMS only affected BCS. E70 resulted in a higher colostrum yield than E100 and E 90 but immunoglobulin content was not affected (p = 0.759). Cow culling was not affected by E or CMS. It increased from 12.9% to 22.2% and 32.5% for cows with a BCS at parturition lower than 1.5 or between 1.5 and 2.0, or higher than 2 respectively. Calf birth weight was neither affected by E or CMS, but there was an interaction between E and dam age (p = 0.050). Increasing the E restriction tended to reduce calf survival (p = 0.089). Performance of the surviving calves was not affected by E, but suckling calves gained faster than rearing calves (p < 0.001). Beef production by the cow-calf pair was not different between energy levels (p = 0.738), but it was 10.8% lower for E70 than for E100 cows. It is not appropriate to apply an E restriction of more than 10-20% for maximum cow reproductive traits and calf performance.

Effect of dam factors on milk intake and performance of Belgian Blue suckling calves.

Milk intake data were collected at 4-week intervals from Belgian Blue double-muscled (BBDM) suckling calves up to 16 weeks after birth. Dams were fed at 100%, 90%, 80% or 70% of their energy requirements during a 140-day indoor period from the beginning of December to the end of April (restriction period). Afterwards, cows were turned out on pasture (re-alimentation period). Mean calving date was 3 June, but parturitions were spread over the year. A total of 521 individual milk intake (IMI) and 120 average daily milk intake (AMI, mean of IMI) records were collected. IMI amounted to 7.0 ± 2.2 kg/day and was not affected by energy level during the indoor period. It was highest in May and June. Calves born out of multiparous cows consumed more milk than those born out of primiparous cows (7.4 v. 6.2 kg per day; P = 0.001), while intake tended to be higher in female than in male calves (7.2 v. 6.8 kg per day; P = 0.044). Dam age at calving, parity, post partum weight and body condition were only weakly correlated with AMI (r 0.4). AMI was correlated with pre-weaning live-weight gain (r = 0.807) and weaning weight (r = 0.783), with a slightly higher correlation for male than for female calves. Daily live-weight gain during the suckling period was increased by 79 g per extra kg daily milk intake on average, and by 86 and 74 g, respectively, for male and female calves. Calf solid feed intake was low, even when milk intake was low. In terms of net energy intake, milk was only substituted for solid feed by 29%. It can be concluded from the calf intake that milk production in BBDM cows is comparable with that of cows from other beef breeds, but its variation is considerable, complicating an accurate estimation.

Effect of energy restriction and re-alimentation in Belgian Blue double-muscled beef cows on digestibility and metabolites.

Four groups of five non-lactating and non-pregnant Belgian Blue double-muscled (BBDM) cows were used to investigate the effect of energy level (E) on digestion, and blood and urine metabolites. The energy levels of the groups, applied indoors during a 140-day restriction period, were 100%, 90%, 80% or 70% of their energy requirements (E100, E90, E80, E70) respectively. Afterwards, animals grazed on the same swards for 203 days (re-alimentation period). Balance trials were conducted at the end of the restriction period (BT1) and at the end of the re-alimentation period (BT2). Blood was sampled at the end of these trials. Diets consisted of maize silage and straw (80/20 on a dry matter basis) and a mineral-vitamin premix, fed at the appropriate E during BT1, or maize silage and a mineral-vitamin premix, fed at 125% of the maintenance requirements, during BT2. Significant increases of the digestibility coefficients were found during BT1 when E decreased, resulting in a better net energy capture of 7% for E70 compared with E100 (p < 0.05). Slightly, but non-significantly higher digestibility coefficients were observed for decreasing E during BT2. Plasma concentrations of glucose and creatinine did not differ between treatments during BT1, while differences were found for triacylglycerols and alpha-amino nitrogen. A tendency for a linear increase was observed for non-esterified fatty acids with decreasing E. Differences in blood metabolite concentrations disappeared in BT2. Urinary creatinine excretion was not affected by E, while body nitrogen loss increased linearly with energy restriction in BT1. No differences were found during BT2, suggesting that non-lactating and non-pregnant BBDM cows are able to adapt to a cyclic change of body weight and body reserves. These data show that restricted cows mobilized body fat as well as body protein. It is concluded that the qualitative aspects of metabolism during energy restriction are comparable in double-muscled cows with those in non-double-muscled animals, although the magnitude of the effects may be different.

Carcass and meat quality in double-muscled Belgian Blue bulls and cows.

Carcass and meat quality of 37 bulls and 91 cows of the Belgian Blue breed (double-muscled type) were compared. Age at slaughter averaged 648±73 and 1820±689 days, respectively. Both groups of cattle were finished on maize silage supplemented with concentrate, and were slaughtered at about 750 kg live weight. Females had a lower (P=0.004) cold carcass weight (469.7 kg) in comparison with bulls (500.8 kg), due to a reduced dressing percentage (63.8 vs. 66.6; P <0.001). SEUROP conformation was better for bulls. SEUROP fat covering (P=0.007) and fat content in the carcass (16.4 vs. 12.9%; P <0.001) and in the M. longissimus thoracis (LT) muscle (2.3 vs. 1.1%; P <0.001) were higher for females than for males. The LT of cows was darker (lower L* and higher a*-value; P <0.001), had a better waterholding capacity (P⩽0.063) and was slightly more tender (P=0.120) than the LT of bulls. Increasing parity reduced dressing percentage and increased LT lightness (L*-value) in cows. Several carcass (SEUROP-grading, composition, LT-area) and meat quality traits (protein and fat contents, drip and cooking losses, a*-value) were better correlated with carcass weight than parity. It is concluded that meat quality of the aged LT of cows is not negatively affected by age, while some carcass quality traits decreased with advancing age. Carcass quality traits adjusted for age at slaughter were better for bulls, but LT meat quality characteristics were at least as good for females as for males.