The effects of nutrition and parity on the development and productivity of Angora goats: 2. Effects of six combinations of mid pregnancy and postnatal nutrition on energy intake and doe live weight, body condition and mohair production

Abstract

There is little research on the nutrient requirements and the effects of nutrient manipulation on the productivity of lactating Angora does. The study design investigated the combined effects of 3 levels of mid pregnancy nutrition (MPN)×2 levels of postnatal nutrition during lactation (PNN) with both single and twin bearing does, providing 6 nutrition patterns. Following artificial insemination and pregnancy scanning, does were fed pelleted rations in individual pens in an outdoor feedlot from day 47 of pregnancy until 13 weeks following kidding. MPN treatments commenced from day 47 as follows: Control (C), fed to lose live weight (–67g/day); Maintenance (M), does fed to maintain live weight; Supplemented (S), does fed to gain live weight at 102g/day. From days 105 of pregnancy until 4days postpartum the feeding level was ad libitum for all treatments. From 4days postpartum PNN treatments were: ad libitum (AL) to allow maximum ME intake; Restricted (R) to 70% of AL. This report is concerned with the responses from kidding to weaning for energy intake, live weight, body condition score (BSC) and mohair production. In AL treatments, maximum ME intake was reached during weeks 5–10 of lactation as follows: twin rearing does 3.88×maintenance; single rearing does 3.25×maintenance. No interaction occurred between MPN and PNN in affecting doe live weight. PNN significantly affected doe live weight from week 2 until weaning with AL does gaining 97g/day from kidding to week 5 and thereafter 28g/day. R fed does lost 40g/day from kidding to week 10 and thereafter gained 38g/day. By week 4 of lactation twin rearing does were 4kg lighter than single rearing does. The change in BCS from just prior to kidding to day 90 of lactation was affected by an interaction between MPN and PNN. BSC of does fed M-R and S-R declined to a greater extent than does fed C-R, while the BCS for C-AL and M-AL increased to that of S-AL, which had remained constant at a high BCS. By day 21 of lactation the effects of PNN were significant, with AL does having significantly higher BCS than R does and the differences increased as lactation progressed. The BCS of single rearing does fed AL increased progressively, while the BCS of all other does declined. By the end of lactation, R does had significantly lower BCS than twin rearing does fed AL, which in turn had a significantly lower BCS compared with single rearing AL fed does. Significant interactions between MPN and PNN affected mohair growth, clean washing yield, mohair fibre diameter, incidence of medullated non kemp fibres and staple length. For fleece weight, S-AL and M-AL had heavier greasy and clean fleece weight compared with S-R and M-R with the other treatments intermediate. Similarly, the mean fibre diameter of S-AL was 2.4μm coarser than that of M-R, with other treatments being intermediate. For both greasy and clean fleece weight, twin rearing does produced 14% less mohair than single rearing does. For R fed twin rearing does, the mohair had greater fibre diameter variability compared with other does. Overall, PNN had a greater number of and larger effects on measured parameters than MPN. Restricting nutrition in lactation was shown to depress doe live weight, BCS and the growth of mohair. Lactating Angora does rapidly changed their live weight and BCS in response to ME provision. To maintain live weight during lactation ME intakes of 3×maintenance were required. Twin rearing does required an additional 0.5×maintenance ME requirement compared with single rearing does. Does can gain live weight and BCS during lactation provided they are fed sufficiently. The preferred nutritional practice should allow maximum ME intake at least until week 6 of lactation.