Liveweight prediction from hip height, condition score, fetal age and breed in tropical female cattle

Abstract

Hip height, body condition, subcutaneous fat, eye muscle area, percentage Bos taurus, fetal age and diet digestibility data were collected at 17 372 assessments on 2181 Brahman and tropical composite (average 28% Brahman) female cattle aged between 0.5 and 7.5 years of age at five sites across Queensland. The study validated the subtraction of previously published estimates of gravid uterine weight to correct liveweight to the non-pregnant status. Hip height and liveweight were linearly related (Brahman: P < 0.001, R2 = 58%; tropical composite P < 0.001, R2 = 67%). Liveweight varied by 12–14% per body condition score (5-point scale) as cows differed from moderate condition (P < 0.01). Parallel effects were also found due to subcutaneous rump fat depth and eye muscle area, which were highly correlated with each other and body condition score (r = 0.7–0.8). Liveweight differed from average by 1.65–1.66% per mm of rump fat depth and 0.71–0.76% per cm2 of eye muscle area (P < 0.01). Estimated dry matter digestibility of pasture consumed had no consistent effect in predicting liveweight and was therefore excluded from final models. A method developed to estimate full liveweight of post-weaning age female beef cattle from the other measures taken predicted liveweight to within 10 and 23% of that recorded for 65 and 95% of cases, respectively. For a 95% chance of predicted group average liveweight (body condition score used) being within 5, 4, 3, 2 and 1% of actual group average liveweight required 23, 36, 62, 137 and 521 females, respectively, if precision and accuracy of measurements matches that used in the research. Non-pregnant Bos taurus female cattle were calculated to be 10–40% heavier than Brahmans at the same hip height and body condition, indicating a substantial conformational difference. The liveweight prediction method was applied to a validation population of 83 unrelated groups of cattle weighed in extensive commercial situations on 119 days over 18 months (20 917 assessments). Liveweight prediction in the validation population exceeded average recorded liveweight for weigh groups by an average of 19 kg (~6%) demonstrating the difficulty of achieving accurate and precise animal measurements under extensive commercial grazing conditions.

Growth of Brahman cross heifers to 2 years of age in the dry tropics

“…A feature of this research was that skeletal growth, a function of bone elongation, continues while losing soft body tissue, also reported by Fordyce et al (2013). This occurred during both the first and second dry seasons after weaning when reductions of up to two body condition score units were seen.…”

Risk factors affecting the reproductive outcome of beef breeding herds in North Australia

“…The difference in P4M for second-lactation cows was not statistically significant. The majority of skeletal and muscle growth for cows occurs within 4.5 years from birth (Fordyce et al 2013a) and therefore, first-lactation cows are likely to have reduced ability to mobilise tissue reserves to meet the additional nutritional requirements associated with lactation. These findings further strengthen the recommendation by Miller et al (1997) that "Growing heifers and first-calf cows should be targeted for aggressive and comprehensive phosphorus management".…”

“…The majority of growth for cows occurs within 4.5 years of age when they mature skeletally (Fordyce et al 2013a). …”

“…Enrolled heifer cohorts were mustered once a year for pregnancy diagnosis and when they calved for the first time they were reclassified as first-lactation cows. At a study animal's first muster information on estimated percentage of Bos indicus, content, year brand and hip height (Fordyce et al 2013a) were recorded. At each muster, body condition score (Gaden et al 2005), lactation status were assessed and recorded.…”

“…At a study animal's first muster information on estimated percentage of Bos indicus, year brand and hip height (Fordyce et al 2013a) were captured. At each muster, body condition score (1-5 scale) (Gaden et al 2005), lactation status were assessed and recorded, and wherever possible liveweight recorded.…”