Breed and heterosis effects for milk yield traits at different production levels, lactation number and milking frequencies

Figures & data

Table 1. Number of herds and lactations, and mean of milk solids (kg/cow) by production level and milking frequency.

Milking frequency	Production level	Number of herds	Number of lactations	Milk solids^a (kg/cow)
OAD	Low	110	30,126	203.6
	Medium	141	60,165	269.2
	High	47	34,329	339.9
TAD	Low	168	62,960	272.7
	Medium	150	86,761	353.8
	High	32	44,910	434.1

^aDefined as the sum of fat and protein yields.

Table 2. Predicted means and SEM of production traits for Holstein-Friesian (F), Jersey (J) and first cross (F₁) F × J cows and estimates of breed and heterosis effects by milking frequency and lactation number.

Lactation number	MF	F	F1F × J	J	Breed effect	Heterosis effect
					F–J (kg)	kg*	%**
Milk yield (kg/cow)
1	OAD	2402 ± 26	2343 ± 25	2075 ± 26	327^a ± 14	105^a ± 11	4.7
1	TAD	3345 ± 21	3224 ± 21	2822 ± 22	523^b ± 12	141^a ± 9	4.6
2	OAD	3105 ± 26	3024 ± 25	2610 ± 26	495^a ± 13	167^a ± 11	5.8
2	TAD	4063 ± 21	3827 ± 21	3267 ± 22	796^b ± 12	162^a ± 9	4.4
3	OAD	3486 ± 26	3349 ± 25	2868 ± 26	618^a ± 13	172^a ± 11	5.4
3	TAD	4520 ± 21	4203 ± 21	3547 ± 22	973^b ± 12	170^a ± 9	4.2
4	OAD	3689 ± 26	3552 ± 25	2978 ± 26	711^a ± 14	219^a ± 12	6.6
4	TAD	4741 ± 21	4360 ± 21	3637 ± 22	1104^b ± 12	171^b ± 10	4.1
5	OAD	3813 ± 27	3605 ± 25	3004 ± 26	809^a ± 15	197^a ± 14	5.8
5	TAD	4821 ± 22	4441 ± 21	3670 ± 22	1151^b ± 13	196^a ± 11	4.6
Fat yield (kg/cow)
1	OAD	117.7 ± 1.3	122.5 ± 1.2	115.6 ± 1.3	2.1^a ± 0.7	5.8^a ± 0.6	5.0
1	TAD	152.0 ± 1.0	162.4 ± 1.0	151.1 ± 1.1	0.9^a ± 0.6	10.9^b ± 0.5	7.2
2	OAD	147.9 ± 1.3	156.4 ± 1.2	147.3 ± 1.3	0.6^a ± 0.7	8.8^a ± 0.6	6.0
2	TAD	182.9 ± 1.0	193.4 ± 1.0	179.5 ± 1.1	3.4^b ± 0.6	12.2^b ± 0.5	6.7
3	OAD	163.8 ± 1.3	173.6 ± 1.2	163.0 ± 1.3	0.8^a ± 0.7	10.2^a ± 0.6	6.2
3	TAD	202.7 ± 1.0	211.7 ± 1.0	196.5 ± 1.1	6.2^b ± 0.6	12.1^a ± 0.5	6.1
4	OAD	171.5 ± 1.3	183.5 ± 1.2	169.5 ± 1.3	2.0^a ± 0.7	13.0^a ± 0.7	7.6
4	TAD	212.2 ± 1.0	220.7 ± 1.0	202.4 ± 1.1	9.8^b ± 0.6	13.4^a ± 0.5	6.5
5	OAD	176.2 ± 1.3	185.5 ± 1.2	171.2 ± 1.3	5.0^a ± 0.8	11.8^a ± 0.8	6.8
5	TAD	215.8 ± 1.1	225.0 ± 1.0	204.4 ± 1.1	11.4^b ± 0.7	14.9^b ± 0.6	7.1
Protein yield (kg/cow)
1	OAD	91.7 ± 1.0	92.4 ± 1.0	84.4 ± 1.0	7.3^a ± 0.5	4.3^a ± 0.4	4.9
1	TAD	121.4 ± 0.8	122.4 ± 0.8	110.2 ± 0.8	11.2^b ± 0.5	6.6^b ± 0.3	5.7
2	OAD	118.6 ± 1.0	121.0 ± 1.0	108.9 ± 1.0	9.7^a ± 0.5	7.3^a ± 0.4	6.4
2	TAD	148.6 ± 0.8	148.0 ± 0.8	131.7 ± 0.8	16.9^b ± 0.4	7.9^a ± 0.4	5.6
3	OAD	132.6 ± 1.0	134.4 ± 1.0	120.6 ± 1.0	12.0^a ± 0.5	7.8^a ± 0.4	6.2
3	TAD	164.5 ± 0.8	162.3 ± 0.8	144.0 ± 0.8	20.5^b ± 0.4	8.1^a ± 0.4	5.2
4	OAD	139.2 ± 1.0	142.0 ± 1.0	125.4 ± 1.0	13.8^a ± 0.5	9.7^a ± 0.5	7.3
4	TAD	171.8 ± 0.8	168.3 ± 0.8	148.0 ± 0.9	23.8^b ± 0.5	8.4^a ± 0.4	5.3
5	OAD	143.2 ± 1.0	143.4 ± 1.0	126.3 ± 1.0	16.9^a ± 0.5	8.7^a ± 0.5	6.4
5	TAD	174.2 ± 0.8	171.1 ± 0.8	149.3 ± 0.9	24.9^b ± 0.5	9.3^a ± 0.4	5.8

SEM, standard error of the mean.

MF, milking frequency; OAD, milking once daily; TAD, milking twice daily.

*Expressed as F₁ F × J − ([F + J]/2).

**Expressed as a percentage of heterosis effects relative to the phenotypic average of the parental breeds under milking frequency and lactation number, as appropriate.

^a,bWithin traits and production level, breed and heterosis effects with different superscripts were significantly different between milking frequencies (P < 0.05).

Table 3. Predicted means and SEM of production traits for Holstein-Friesian (F), Jersey (J) and first cross (F₁) F × J cows and estimates of breed and heterosis effects at different production levels.

Production level	MF	F	F1 F × J	J	Breed effect	Heterosis effect
					F–J (kg)	kg*	%**
Milk yield (kg/cow)
L	OAD	2554 ± 25	2499 ± 23	2178 ± 25	376^a ± 18	133^a ± 14	5.6
	TAD	3529 ± 17	3351 ± 16	2843 ± 18	686^b ± 13	165^a ± 10	5.2
M	OAD	3313 ± 20	3221 ± 19	2770 ± 20	543^a ± 13	179^a ± 10	5.9
	TAD	4471 ± 17	4174 ± 16	3577 ± 18	894^b ± 12	150^a ± 9	3.7
H	OAD	4184 ± 28	3903 ± 27	3369 ± 17	815^a ± 16	126^a ± 13	3.3
	TAD	5548 ± 26	5139 ± 26	4247 ± 28	1301^b ± 16	241^b ± 13	4.9
Fat yield (kg/cow)
L	OAD	121.3 ± 1.2	128.7 ± 1.1	120.2 ± 1.2	1.1^a ± 0.9	7.9^a ± 0.7	6.5
	TAD	158.8 ± 0.8	167.3 ± 0.8	154.6 ± 0.9	4.2^b ± 0.6	10.6^b ± 0.5	6.8
M	OAD	157.7 ± 1.0	167.1 ± 0.9	156.5 ± 0.9	1.2^a ± 0.6	10.0^a ± 0.5	6.4
	TAD	202.8 ± 0.8	212.4 ± 0.8	198.1 ± 0.8	4.7^b ± 0.6	11.9^a ± 0.4	5.9
H	OAD	195.5 ± 1.3	203.1 ± 1.3	192.0 ± 1.3	3.5^a ± 0.8	9.3^a ± 0.6	4.8
	TAD	246.8 ± 1.2	258.4 ± 1.2	238.1 ± 1.3	8.7^b ± 0.8	15.9^b ± 0.6	6.6
Protein yield (kg/cow)
L	OAD	97.3 ± 1.0	99.0 ± 0.9	88.9 ± 0.9	8.4^a ± 0.6	5.9^a ± 0.5	6.3
	TAD	127.7 ± 0.7	127.6 ± 0.6	113.1 ± 0.7	14.6^b ± 0.5	7.2^a ± 0.3	6.0
M	OAD	126.4 ± 0.8	128.6 ± 0.7	115.3 ± 0.7	11.1^a ± 0.5	7.7^a ± 0.4	6.4
	TAD	163.2 ± 0.6	161.4 ± 0.6	144.1 ± 0.7	19.1^b ± 0.4	7.7^a ± 0.3	5.0
H	OAD	158.9 ± 1.1	156.8 ± 1.0	141.5 ± 1.1	17.4^a ± 0.5	6.6^a ± 0.4	4.4
	TAD	203.2 ± 1.0	199.0 ± 1.0	173.9 ± 1.0	29.3^b ± 0.6	10.4^b ± 0.4	5.5

SEM, standard error of the mean.

H, high milk solids yield; L, low milk solids (fat + protein) yield; M, medium milk solids yield; MF, milking frequency; OAD, milking once daily; TAD, milking twice daily.

*Expressed as F₁ F × J − ([F + J]/2).

**Expressed as a percentage of heterosis effects relative to the phenotypic average of the parental breeds under milking frequency and production levels, as appropriate.

^a,bWithin traits and production level, breed and heterosis effects with different superscripts were significantly different between milking frequencies (P < 0.05).