5. Analyses of dairy production data from Mikolongwe livestock unit

Introduction
Mikolongwe livestock unit
Reproductive performance
Productive performance
Dairy productivity

Introduction

The Mikolongwe livestock unit supplies Friesian bulls for the production of F1 crossbred cows at Chizombezi (see Figure 2). Analysis of production records from Mikolongwe livestock unit provides useful information about the expected performance of crossbred cows produced from Friesian bulls and 'off-type' females.

Mikolongwe livestock unit

Management practices

The Mikolongwe livestock station was founded in the early 1930s as a private estate. The government took over the estate in the early 1950s to serve as a centre for livestock and poultry improvement. The station was essentially a multiplication centre, while the Chizombezi, Chikowa and Tuchila substations, which are part of Mikolongwe, either bred or reared animals.

Dairying activities started in Mikolongwe and the substations in 1973. The Mikolongwe livestock station maintains a milking herd of pure-Friesian cattle and supplies Friesian bulls to Chizombezi station, which produces crossbred heifers for smallholder dairy farms.

Management practices

Pure-Friesian heifers were inseminated for the first time when they attained a minimum weight of 320 kg at about 18 months of age. Heifers and cows in their seventh month of pregnancy were 'steamed up' until calving. Pregnant heifers also received training in milking-shed practices. Cows and heifers in the last two weeks of pregnancy were separated from the herd and went into calving boxes. The calf stayed with the dam for 48 hours. The dam was not milked on the first day, but on the second day the dam was milked after the calf had been suckled. From the third day calves were separated from the dams and artificially reared, receiving 4 kg of milk/day. Calves were fed with either milk diluted with water or skim milk in addition to calf ration from the second week until weaning at 16 weeks of age. The calves received calf-ration supplements until 20 weeks of age, after which they grazed and received silage and hay supplements during the dry season. Bull calves were not castrated unless they showed signs of abnormalities. All heifers joined the breeding herd except those that showed abnormalities such as blindness or loss of teat. Culling took place after the first calving.

The cows were milked twice daily. Milk was weighed for each cow at each milking. Calves were weighed both at birth and at weaning. All animals were dewormed at 3 month intervals. Cattle were dipped against ticks once every week in a solution of Supona. The major health problem was eye infection. Post-weaning mortality among calves was about 10%.

The dairy cattle herd at Mikolongwe as of May 1984 comprised 60 milking cows, 15 heifers of breeding age, 39 young heifers and 50 calves.

Reproductive performance

Calving interval and days open

Calving interval and days open

The means for calving interval and days open for 213 carvings at Mikolongwe were 470 ± 145 days and 192 ± 148 days, respectively, with corresponding CVs of 32 and 77%.

Analyses of variance of calving interval and days open are presented in Table 31.

Only lactation number or parity had a significant effect (P < 0.05) on calving interval and days open (Table 31).

The estimated least squares means for calving interval and days open are laid out in Table 32.

Calving intervals were longer after the fourth parity.

Table 31. Analyses of variance of calving interval and days open at Mikolongwe, 1974-83.

Source	Calving interval		Days open
	d.f.	MS x 10-1	d.f.	MS x 10-1
Lactation number	5	5 447*	4	6 168*.
Year of calving	8	3 596	8	3 754
Month of calving	11	3 419	11	3 184
Remainder	188	2 200	189	2 201

* = P<0.05

Table 32. Estimated least squares mean for calving interval and days open at Mikolongwe, 1974-83.

Variable	No.	Calving interval (days)	No.	Days open
Overall	213	481	213	192
Lactation number
1	42	438 a	41	159 a
2	47	469 ab	47	193 a
3	37	495 ac	36	215 a
4	29	424a	30	148a
5	22	538 bc	59	246 b
6+	36	521 bc
Year of calving
1974	31	545	31	258
1975	32	513	32	226
1976	22	499	22	213
1977	19	495	19	200
1978	27	473	27	188
1979	26	496	26	208
1980	18	420	18	131
1981	27	427	27	136
1982	11	460	11	169
Month of calving
January	17	484	17	195
February	26	439	26	154
March	27	475	27	187
April	23	388	23	102
May	28	427	28	141
June	19	496	19	208
July	12	454	12	165
August	5	580	5	292
September	10	514	10	224
October	11	502	11	212
November	19	539	19	248
December	16	473	16	178

Within variable groups, row means followed by the same letter do not differ significantly (P < 0.05). No letter following indicates that the variable group did not show a significant difference in the analysis of variance.

Productive performance

Total lactation yield, lactation length, milk yield per day of lactation and dry period

Total lactation yield, lactation length, milk yield per day of lactation and dry period

The means for total lactation yield, lactation length, yield per lactation day and dry period for the Friesian herd at Mikolongwe were 3407 ± 1241 kg, 354 ± 110 days, 9.3 ± 2.4 kg and 101 ± 103 days, respectively, with corresponding CVs of 36,31,26 and 102%. Analyses of variance for the four traits are presented in Table 33.

Lactation number or parity had significant effects on total lactation yield (P < 0.05), yield per lactation day (P < 0.01) and dry period

(P < 0.05) but not on lactation length. Year of calving significantly influenced lactation yield, yield per lactation day and lactation length (P < 0.01) but not dry period. Month of calving had a significant effect only on yield per lactation day (P < 0.05) (Table 33).

The estimated least squares means for the four characters are displayed in Table 34.

The fifth lactation gave the highest total yield, but yield per lactation day was highest during the fourth lactation (Table 34).

Total lactation yield and yield per lactation day have been declining since 1979. Total milk yields in 1980,1981,1982 and 1983 were 17,56,59 and 69% lower than the mean, respectively. The same trend was found in yield per lactation day.

Dairy productivity

Annual milk yield per cow

Annual milk yield per cow

The mean annual milk yield per cow was 3077 ± 960 kg, with a CV of 31%.

Analysis of variance for annual milk yield is shown in Table 35.

Lactation number and year of calving had significant effects (P < 0.01) on annual milk yield per cow.

The estimated least squares means for annual milk yield per cow are presented in Table 36.

Annual milk yield per cow generally increased with increasing parity number and peaked during the fourth lactation as a result of the shorter calving interval associated with the fourth lactation. The pattern of influence of year of calving on annual milk yield was the same as on the total lactation yield and yield per lactation day, i.e. a drastic drop in milk yields from 1980 onwards. The decline in production coincided with deficiencies in feed supply as a result of poor weather during this period.

Table 33. Analyses of variance of total lactation milk yield, lactation length, milk yield per day of lactation and dry period for pure-Friesian cows at Mikolongwe, 1974-83.

Source	d.f.	Lact. yield	Lact. length	Yield/day	d.f.	Dry period
		MS x 104	MS x 10-2	MS x 10		MS x 10-1
Lactation number	5	387*	107	448**	4	2 688*
Year of calving	9	8 155**	1 033**	4 024**	8	1 498
Month of calving	11	177	112	130*	11	1 411
Remainder	322	154	119	57	189	1 079

* = P<0.05
** = P<0.01

Table 34. Estimated least squares means for total lactation milk yield, lactation length, milk yield per day of lactation and dry period of pure-Friesian cows at Mikolongwe, 1974-83.

Variable	No.	Lact. Yield (kg)	Lact. Length (days)	Milk yield/ day (kg)	No.	Dry period (days)
Overall	348	3 515	354	9.7	213	99
Lactation number
1	75	3 001 a	367	8.0 a	41	70 a
2	72	3 555 bc	355	9.7 bc	47	93 ab
3	59	3 620 c	348	9.9c	37	113 ab
4	43	3 593 bd	337	10.8 de	30	83a
5	32	3 772 be	379	9.7 be	50	134b
6+	67	3 547 bc	339	10.0 bc
Year of calving
1974	38	4 864 ag	401 ag	12.7 ac	32	146
1975	35	4 559 ab	391 ac	11.8 ab	31	117
1976	29	5 235 g	448 g	11.9 ab	22	87
1977	25	4 958 ag	365 ab	13.7c	19	108
1978	32	4 000 b	375 ac	10.8b	27	77
1979	35	4 525a	384 ac	11.8a	25	77
1980	43	2 931c	319 bd	9.3c	19	70
1981	47	1 551 de	344 cb	4.5 de	27	89
1982	43	1 442 ef	285 de	4.9 ef	11	117
1983	21	1 083 f	231e	5.4f
Month of calving
January	29	3 714	370	9.4 ace	17	89
February	27	3 412	318	10.1 abe	25	117
March	38	3 657	344	10.7 bde	27	115
April	40	3 732	364	10.1 abe	21	49
May	50	3 731	365	9.9 abe	29	60
June	25	3 675	359	10.2 ade	19	98
July	20	3 655	344	10.3 ad	12	89
August	19	3 699	383	9.4 af	5	98
September	18	3 376	327	10.0 af	11	140
October	25	2 902	347	8.3c	11	104
November	26	3 511	386	8.8 cef	20	142
December	21	3 112	349	8.9 ac	16	83

Within variable groups, row means followed by the same letter do not differ significantly (P < 0.05). No letter following indicates that the variable group did not show a significant difference in the analysis of variance.

Table 35. Analysis of variance of annual milk yield per cow for pure-Friesian cows at Mikolongwe, 1974-83.

Source	d.f.	MS x 10-4
Lactation number	5	292* *
Year of calving	8	2 256* *
Month of calving	11	162
Remainder	205	92

** = P<0.01

Table 36. Estimated least squares means for annual milk yield per cow for pure-Friesian cows at Mikolongwe, 1974-83.

Variable	No.	Annual milk yield (kg)
Overall	230	3 002
Lactation number
1	52	2 540 a
2	51	3 045 bf
3	40	2 897 ab
4	29	3 432 cf
5	22	3 100 cbd
6+	36	2 998 cbe
Year of calving
1974	32	3 802 ag
1975	32	3 431 ab
1976	22	3 697 afg
1977	19	4 027 g
1978	27	3 240 bf
1979	26	3 670 afg
1980	30	2 598 c
1981	31	1 360 d
1982	11	1 194 de
Month of calving
January	18	3 127
February	28	3 067
March	29	3 208
April	24	3 578
May	30	3 293
June	19	3 099
July	15	2 957
August	6	2 882
September	11	3 037
October	12	2 517
November	22	2 676
December	16	2 584

Within variable groups, row means followed by the same letter do not differ significantly (P < 0.05). No letter following it indicates that the variable group did not show a significant difference in the analysis of variance.