Cattle productivity

Indices of cow productivity
Herd productivity

Indices of cow productivity

The characters of reproductive performance, calf viability, calf 9 month weight and cow weight were combined to build three productivity indices. Index 1, the weight of 9 month old calf per cow per year, was computed for each cow parturition as the product of weight of 9 month old calf × 365 ÷ interval to next parturition. Index 2, the weight of 9 month old calf per 100 kg of cow per year, was computed as index 1 ÷ cow average weight × 100. Index 3, the total weight of 9 month old calf per 100 kg of metabolic weight of cow per year, was computed as Index 1 ÷ cow average weight ^.73 × 100. Data on 280 parturitions were available from 1974 to 1980.

The significance of environmental influences on the three productivity indices is indicated in Table 52.

Table 52. Analysis of variance of productivity indices

Source	d.f.	Mean squares
		Index 1	Index 2	Index 3
Origin	1	1998	76	26
Year of calving	6	5122**	879**	168**
Month of calving	11	2333**	360**	70**
Number of calving	3	3425**	184	53
Sex	1	964	143	29
Remainder	257	880	149	28

** = P< 0.01.

The estimated least squares means for productivity indices are laid out in Table 53.

Table 53. Estimated least squares means for productivity indices

Variable	Number	Index 1	Index 2	Index 3
Overall mean	280	70.1	29.1	127
Origin
Foundation (1)	224	65.2	28.2	122
Born on centre (2)	56	75.1	30.1	133
Year of calving
1974	22	95.7	38.7	171
1975	23	66,7	27.8	121
1976	49	63.2	26.2	114
1977	41	82.5	34.7	151
1978	68	66.3	29.5	127
1979	57	74.4	30.0	132
1980	20	42.1	16.9	74
Month of calving
January	10	61.4	26.4	114
February	10	60.1	22.5	101
March	17	89.6	35.8	158
April	25	83.7	33.6	148
May	65	78.2	32.4	142
June	27	66.9	29.2	126
July	17	73.9	30.2	133
August	20	54.4	22.6	99
September	21	55.1	24.7	105
October	26	80.2	34.7	150
November	29	73.6	30.1	132
December	13	64.3	27.3	119
Number of calving
1	75	56.7	26.0	110
2	78	66.7	28.4	123
3	66	77.1	30.7	136
4+	61	80.0	31.4	139
Sex
Male	157	72.1	29.9	131
Female	123	68.2	28.4	124

The mean productivity indices were:

Index 1.	70.1 kg of 9 month old calf per cow per year
Index 2.	29.1 kg of 9 month old calf per 100 kg of cow per year
Index 3.	127 kg of 9 month old calf per 100 kg .73 of cow per year.

Year and month of calving had very significant effects on productivity. This would be expected, following the major year and month effects previously found on the different performance traits making up the productivity indices.

The effect of calving number was significant on index 1 only, cows with three or more carvings being 15% more productive than second carvers and 27% more productive than first carvers.

Herd productivity

Adjustment of the three cow productivity indices to account for cow viability (97.1%) give the most accurate estimates of overall herd productivity.
These are:

Index 1:	67.6 kg of 9 month old calf per cow per year
Index 2:	28.1 kg of 9 month old calf per 100 kg of cow per year
Index 3:	123 kg of 9 month old calf per 100 kg .73 of cow per year.