Effects of photoperiod and feeding whole maize, whole barley, or rolled barley on growth performance and diet digestibility in veal calves

Abstract

Fifty-seven black and white male dairy calves, reared from 48 to 222 kg liveweight, were used to study the effects of photoperiod and feeding whole maize (75%; WM), whole barley (80%; WB) or rolled barley (80%; RB) based diet after weaning. Photoperiod treatments were 10 h of light (L):14 h of dark (D), 16L:8D, 10L:14D for 6 weeks then followed by 16L:8D, or 16L:8D for 6 weeks then followed by 10L:14D. During weeks 17 and 20, 30 calves of uniform weight, ten per feeding treatment, underwent two digestibility trials. Exposure to 16L:8D photoperiod or a change from 16L:8D to 10L:14D increased similarly weight gain by 6.6% and feed intake by 9.5% without affecting feed efficiency. Calves fed WM consumed less feed (P < 0.05), had similar average daily gain (ADG) and were 25% more efficient than calves fed WB but calves fed RB had a lower average daily feed intake (P < 0.05), had similar ADG and were 10% more efficient than WB-fed calves. Calves fed RB had a tendency to have higher (P = 0.07) carcass weight and dressing percentage (118.8 kg and 53.6%, respectively) than calves fed WB (115.4 kg and 52.0%, respectively). Body and meat composition, meat color, and haematocrit and haemoglobin levels were not significantly affected by feeding or photoperiod treatments. Digestibility of dry matter (DM), energy (E), nitrogen, starch (S), phosphorus (P) and copper (Cu) were higher (P < 0.05) for calves fed WM compared to those fed WB. Furthermore, digestibility of DM, E, S, P and Cu were reduced (P < 0.05) in the diet containing WB compared to the diet containing RB. Diet did not affect energy intake even though, when expressed as a percentage of energy intake, calves fed WM retained more E (P < 0.05) than those fed WB (77.2 vs 64.7%) and calves fed RB had a higher E retention (69.8%) than those fed WB. Nitrogen intake and excretion were higher (P < 0.05) for the calves fed WB compared to those fed WM; there was no significant difference between both barley diets. Nitrogen retention was not affected by the diets. Blood urea level of calves fed WB was also 28.8% higher than blood urea level of calves fed WM. There was no significant effect of photoperiod treatments on diet digestibility, E and N retentions, and blood urea levels nor was there any significant interaction with diet treatments except on body weight changes. In conclusion, our results indicated positive effects of long-day photoperiod on growth performance but also showed evidence of photorefractoriness to subsequent photoperiod exposure. There was no effect of photoperiod on feed digestibility and feed efficiency. Digestibility and energy retention were lower with whole barley as compared with whole maize diet but were improved by rolling barley thus improving feed efficiency.