Msangi B S J, Bryant M J, Thorne P J
Livestock Research Centre, Tanga, Tanzania.
Trop Anim Health Prod. 2005 Jul;37(5):403-12. doi: 10.1007/s11250-005-6854-7.
A 2-year longitudinal survey was carried out to investigate factors affecting milk yield in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of milk yield, body condition score (BCS) and heart girth measurements were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in milk yield were investigated using a general linear model by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. Daily milk yield (including milk sucked by calves) was determined by calving year (p < 0.0001), calf rearing method (p = 0.044) and BCS at calving (p < 0.0001). Only BCS at calving contributed to variation in volume of milk sucked by the calf, lactation length and lactation milk yield. BCS at 3 months after calving was improved on farms where labour was hired (p = 0.041) and BCS change from calving to 6 months was more than twice as likely to be negative on U than SU and PU farms. It was concluded that milk production was predominantly associated with BCS at calving, lactation milk yield increasing quadratically from score 1 to 3. BCS at calving may provide a simple, single indicator of the nutritional status of a cow population.
开展了一项为期两年的纵向调查，以研究影响城市中心及周边小农户饲养的杂交奶牛产奶量的因素。每隔约两周走访60个农场，收集产奶量、体况评分（BCS）和胸围测量的详细数据。15个农场在城镇内（U），23个农场距离城镇约5公里（SU），22个农场距离城镇约10公里（PU）。采用一般线性模型，通过逐步向前选择和向后剔除方法来判断重要自变量，从而研究产奶量的变异来源。模型构建第一步考虑的因素包括位置（PU、SU和U）、产犊季节、产犊时、产后3个月和产后6个月的BCS、产犊年份、畜群规模类别、劳动力来源（雇佣劳动力和家庭劳动力）、犊牛饲养方法（桶饲和部分哺乳）以及奶牛的胎次。日产奶量（包括犊牛吸吮的奶量）由产犊年份（p<0.0001）、犊牛饲养方法（p = 0.044）和产犊时的BCS（p<0.0001）决定。只有产犊时的BCS会影响犊牛吸吮的奶量、泌乳期长度和泌乳期产奶量的变化。在雇佣劳动力的农场，产后3个月的BCS有所改善（p = 0.041），且城镇内农场从产犊到6个月时BCS下降的可能性是距离城镇5公里和10公里农场的两倍多。研究得出结论，产奶量主要与产犊时的BCS相关，泌乳期产奶量从评分1到3呈二次方增加。产犊时的BCS可能是奶牛群体营养状况的一个简单单一指标。
