The effects of mid pregnancy and postnatal nutrition, birth parity and sex on Angora goat live weight gain, skin follicle development, mohair physical properties and fleece value

Abstract

There is little information on permanent effects of nutritional manipulation of Angora does on the development of skin follicles of their progeny in utero and during the early postnatal period. This report investigates the combined effects of 3 levels of mid pregnancy nutrition (MPN) × 2 levels of postnatal nutrition during lactation (PNN) on skin follicle development and the subsequent physical properties and value of mohair until 19 months of age. Does were housed in individual pens in an outdoor feedlot from day 47 of pregnancy until 13 weeks postpartum. Kids grazed pasture following weaning at 16 weeks. MPN treatments commenced from day 47 as follows: Control (C), does fed to lose live weight (−67 g/d); Maintenance (M), does fed to maintain live weight; Supplemented (S), does fed to gain live weight at 102 g/d. From days 105 of pregnancy until 4 days postpartum the feeding level was ad libitum for all treatments. From 4 days postpartum PNN treatments were: ad libitum (AL) to allow maximum ME intake resulting in doe live weight gain throughout lactation; Restricted (R) to 70% of AL, resulting in doe live weight loss until week 10 of lactation. Kid skin biopsy samples were taken at birth, 114, 180 and 420 days of age. Fleeces were harvested at 7, 13 and 19 months of age and tested for physical properties. Commercial value of mohair was determined using known price discount responses and measured mean fibre diameter (MFD). Improving MPN increased kid live weight up to 6 months of age. Improving PNN increased kid live weight between 1–6 months of age. The ratio of secondary to primary skin follicles increased from 2.56 ± 0.83 at birth to 9.32 ± 1.41 at 4 months of age. The density of secondary follicles, total secondary follicle number and ratio of secondary to primary follicles were affected by significant interactions between MPN and PNN, with treatments S-AL, C-AL and M-R being higher than other treatments. Improving PNN increased total greasy and clean mohair production by 5%. Average MFD was affected by interactions between MPN and PNN, with treatment S-AL having mohair 1.8 μm finer than S-R and C-AL. Improving both MPN and PNN reduced lifetime MFD. Staple length was affected by interactions between MPN and PNN, treatments with the finest mohair having shorter staples. The first fleece weight was affected by birth parity and sex of progeny, but not subsequent fleeces. The MFD of the second and third fleeces for female kids were 0.9–2.2 μm coarser compared with male kid fleeces. Interactions between MPN and PNN affected lifetime fleece value with S-AL producing 20% higher value fleeces compared with other treatments. There are preferred nutritional combinations for breeding Angora does which permanently increase the skin follicle population and consequently improve the lifetime physical properties and value of the mohair grown by their progeny.