The importance of a high feed intake during lactation of primiparous sows nursing large litters.

The objective of this study was to investigate whether nursing a large number of piglets has negative effects on lactation and postweaning performance of primiparous sows and whether a greater lactation feed intake can prevent possible negative effects. Data were recorded on 268 ad libitum-fed sows of three genotypes (G1, G2, and G3) in an experiment where litter size was standardized to 8, 11, or 14 piglets during a 4-wk lactation. Compared to G1 and G2, G3 sows were heavier (P < 0.05) and leaner (P < 0.05) at weaning of their litters, lost similar amounts of BW and backfat, and their piglets grew faster (P < 0.05). Compared to G1, feed intake during lactation was higher for G3 sows (P < 0.05), and their risk of a prolonged weaning-to-estrus interval was lower (P < 0.01). Daily feed intake by sows was not affected by litter size in G1 and G3, but it was quadratically affected in G2 (P < 0.05), with a maximum at 10.8 piglets. Backfat loss of the sows increased linearly with litter size (P < 0.05) in G1 and G3. In G2, backfat loss increased only at litter sizes > 9.8 piglets (P < 0.01). Body weight loss of the sow and litter weight gain increased linearly with litter size (P < 0.001). Per extra piglet nursed, sows had a 23% (P < 0.01) higher probability of a prolonged weaning-to-estrus interval. A higher daily feed intake during lactation reduced tissue loss of the sow, increased litter weight gain (P < 0.01), and reduced the probability of a prolonged weaning-to-estrus interval (by 42% per extra kilogram; P < 0.01). Sows with a lower daily body weight loss during first lactation had a larger second litter (1.28 piglets/kg; P < 0.01), and their probability of a prolonged weaning-to-estrus interval was reduced by 61% per kilogram (P < 0.001). With increasing litter size, it is therefore recommended to reduce body weight loss during lactation by stimulating daily feed intake and by genetic selection.

Effect of melatonin and lighting schedule on energy metabolism in broiler chickens.

The effect of melatonin and lighting schedule on energy metabolism in broiler chickens was studied. Eight groups of six female broiler chickens each were assigned to a continuous lighting schedule [23 h light (L):1 h darkness (D)] or an intermittent lighting schedule (1L:3D), and were fed a diet with or without melatonin (40 ppm). At 21 d of age, the chickens were placed in respiration chambers for 20 d. Energy and nitrogen balances, heat production, and physical activity were measured per group. The only effect of melatonin on energy metabolism, was a decreasing effect on activity-related heat production. The intermittent lighting schedule induced improved feed conversion, higher metabolizability of the diet, and lower physical activity compared to continuous lighting. No interactions between melatonin and lighting schedule were found on energy metabolism traits. Lighting schedule strongly affected daily heat production pattern (total, activity-related, and nonactivity-related heat production). Melatonin had a reducing effect on activity-related heat production during the day, especially during light periods. The present study demonstrated that reduced energy expenditure for physical activity, caused by the supplementation of melatonin to the diet, might be a reason for the often observed improvement of feed conversion. Furthermore, this study showed that feed conversion was improved with an intermittent lighting schedule, which was related to higher metabolizability and lower energy expenditure on physical activity, compared to continuous lighting.